| blob | 52cdafe1ecae044493a60e3c1ef66ccec0322f03 |
6 </pre>
9 <ul>
17 <ul>
19 <ul>
22 </ul>
24 <ul>
29 </ul>
30 </ul>
32 <ul>
35 <ul>
43 </ul>
45 <ul>
48 </ul>
50 <ul>
60 </ul>
62 <!--page 2 -->
63 <ul>
81 </ul>
84 <ul>
93 </ul>
95 <ul>
102 </ul>
104 <ul>
107 </ul>
109 <ul>
116 <!--page 3 -->
120 </ul>
122 <ul>
132 </ul>
133 </ul>
135 <ul>
137 <ul>
142 </ul>
144 <ul>
146 </ul>
148 <ul>
158 </ul>
160 <ul>
163 </ul>
166 <ul>
171 </ul>
174 <ul>
177 <!--page 4 -->
178 </ul>
182 <ul>
185 </ul>
187 <ul>
202 </ul>
204 <ul>
207 </ul>
209 <ul>
212 </ul>
214 <ul>
216 </ul>
220 <ul>
225 </ul>
227 <ul>
236 <!--page 5 -->
239 </ul>
241 <ul>
250 </ul>
252 <ul>
259 </ul>
262 <ul>
266 </ul>
268 <ul>
275 </ul>
276 <li><a href="#7.25"> 7.25 Wide character classification and mapping utilities <wctype.h></a>
277 <ul>
281 </ul>
283 <ul>
293 <!--page 6 -->
297 <li><a href="#7.26.13"> 7.26.13 Wide character classification and mapping utilities <wctype.h></a>
298 </ul>
299 </ul>
301 <ul>
305 </ul>
307 <ul>
331 <li><a href="#B.24"> B.24 Wide character classification and mapping utilities <wctype.h></a>
332 </ul>
337 <ul>
341 <!--page 7 -->
348 </ul>
350 <ul>
358 </ul>
360 <ul>
364 </ul>
367 <ul>
373 </ul>
376 <!--page 8 -->
377 <!--page 9 -->
378 </ul>
382 ISO (the International Organization for Standardization) and IEC (the International
383 Electrotechnical Commission) form the specialized system for worldwide
384 standardization. National bodies that are member of ISO or IEC participate in the
385 development of International Standards through technical committees established by the
386 respective organization to deal with particular fields of technical activity. ISO and IEC
387 technical committees collaborate in fields of mutual interest. Other international
388 organizations, governmental and non-governmental, in liaison with ISO and IEC, also
389 take part in the work.
391 International Standards are drafted in accordance with the rules given in the ISO/IEC
392 Directives, Part 3.
394 In the field of information technology, ISO and IEC have established a joint technical
395 committee, ISO/IEC JTC 1. Draft International Standards adopted by the joint technical
396 committee are circulated to national bodies for voting. Publication as an International
397 Standard requires approval by at least 75% of the national bodies casting a vote.
399 International Standard ISO/IEC 9899 was prepared by Joint Technical Committee
401 their environments and system software interfaces. The Working Group responsible for
402 this standard (WG 14) maintains a site on the World Wide Web at
403 http://www.open-std.org/JTC1/SC22/WG14/ containing additional
404 information relevant to this standard such as a Rationale for many of the decisions made
405 during its preparation and a log of Defect Reports and Responses.
410 <ul>
411 <li> restricted character set support via digraphs and <a href="#7.9"><iso646.h></a> (originally specified
412 in AMD1)
413 <li> wide character library support in <a href="#7.24"><wchar.h></a> and <a href="#7.25"><wctype.h></a> (originally
414 specified in AMD1)
415 <li> more precise aliasing rules via effective type
416 <li> restricted pointers
417 <li> variable length arrays
418 <li> flexible array members
419 <li> static and type qualifiers in parameter array declarators
422 <li> the long long int type and library functions
423 <!--page 10 -->
424 <li> increased minimum translation limits
426 <li> remove implicit int
427 <li> reliable integer division
428 <li> universal character names (\u and \U)
429 <li> extended identifiers
430 <li> hexadecimal floating-point constants and %a and %A printf/scanf conversion
431 specifiers
432 <li> compound literals
433 <li> designated initializers
434 <li> // comments
435 <li> extended integer types and library functions in <a href="#7.8"><inttypes.h></a> and <a href="#7.18"><stdint.h></a>
436 <li> remove implicit function declaration
437 <li> preprocessor arithmetic done in intmax_t/uintmax_t
438 <li> mixed declarations and code
439 <li> new block scopes for selection and iteration statements
440 <li> integer constant type rules
441 <li> integer promotion rules
442 <li> macros with a variable number of arguments
443 <li> the vscanf family of functions in <a href="#7.19"><stdio.h></a> and <a href="#7.24"><wchar.h></a>
445 <li> treatment of error conditions by math library functions (math_errhandling)
448 <li> trailing comma allowed in enum declaration
449 <li> %lf conversion specifier allowed in printf
450 <li> inline functions
453 <li> idempotent type qualifiers
454 <li> empty macro arguments
455 <!--page 11 -->
456 <li> new structure type compatibility rules (tag compatibility)
457 <li> additional predefined macro names
458 <li> _Pragma preprocessing operator
459 <li> standard pragmas
460 <li> __func__ predefined identifier
461 <li> va_copy macro
462 <li> additional strftime conversion specifiers
463 <li> LIA compatibility annex
464 <li> deprecate ungetc at the beginning of a binary file
465 <li> remove deprecation of aliased array parameters
466 <li> conversion of array to pointer not limited to lvalues
467 <li> relaxed constraints on aggregate and union initialization
468 <li> relaxed restrictions on portable header names
469 <li> return without expression not permitted in function that returns a value (and vice
470 versa)
471 </ul>
473 Annexes D and F form a normative part of this standard; annexes A, B, C, E, G, H, I, J,
474 the bibliography, and the index are for information only. In accordance with Part 3 of the
475 ISO/IEC Directives, this foreword, the introduction, notes, footnotes, and examples are
476 also for information only.
477 <!--page 12 -->
481 With the introduction of new devices and extended character sets, new features may be
482 added to this International Standard. Subclauses in the language and library clauses warn
483 implementors and programmers of usages which, though valid in themselves, may
484 conflict with future additions.
486 Certain features are obsolescent, which means that they may be considered for
487 withdrawal in future revisions of this International Standard. They are retained because
488 of their widespread use, but their use in new implementations (for implementation
489 features) or new programs (for language [<a href="#6.11">6.11</a>] or library features [<a href="#7.26">7.26</a>]) is discouraged.
491 This International Standard is divided into four major subdivisions:
492 <ul>
497 </ul>
499 Examples are provided to illustrate possible forms of the constructions described.
500 Footnotes are provided to emphasize consequences of the rules described in that
501 subclause or elsewhere in this International Standard. References are used to refer to
502 other related subclauses. Recommendations are provided to give advice or guidance to
503 implementors. Annexes provide additional information and summarize the information
504 contained in this International Standard. A bibliography lists documents that were
505 referred to during the preparation of the standard.
507 The language clause (clause 6) is derived from ''The C Reference Manual''.
510 <!--page 13 -->
520 This International Standard specifies the form and establishes the interpretation of
521 programs written in the C programming language.<sup><a href="#note1"><b>1)</b></a></sup> It specifies
522 <ul>
523 <li> the representation of C programs;
524 <li> the syntax and constraints of the C language;
525 <li> the semantic rules for interpreting C programs;
526 <li> the representation of input data to be processed by C programs;
527 <li> the representation of output data produced by C programs;
528 <li> the restrictions and limits imposed by a conforming implementation of C.
529 </ul>
531 This International Standard does not specify
532 <ul>
533 <li> the mechanism by which C programs are transformed for use by a data-processing
534 system;
535 <li> the mechanism by which C programs are invoked for use by a data-processing
536 system;
537 <li> the mechanism by which input data are transformed for use by a C program;
538 <li> the mechanism by which output data are transformed after being produced by a C
539 program;
540 <li> the size or complexity of a program and its data that will exceed the capacity of any
541 specific data-processing system or the capacity of a particular processor;
544 <!--page 14 -->
545 <li> all minimal requirements of a data-processing system that is capable of supporting a
546 conforming implementation.
548 </ul>
551 <p><small><a name="note1" href="#note1">1)</a> This International Standard is designed to promote the portability of C programs among a variety of
552 data-processing systems. It is intended for use by implementors and programmers.
553 </small>
557 The following normative documents contain provisions which, through reference in this
558 text, constitute provisions of this International Standard. For dated references,
559 subsequent amendments to, or revisions of, any of these publications do not apply.
560 However, parties to agreements based on this International Standard are encouraged to
561 investigate the possibility of applying the most recent editions of the normative
562 documents indicated below. For undated references, the latest edition of the normative
563 document referred to applies. Members of ISO and IEC maintain registers of currently
564 valid International Standards.
567 use in the physical sciences and technology.
570 interchange.
573 terms.
575 ISO 4217, Codes for the representation of currencies and funds.
577 ISO 8601, Data elements and interchange formats -- Information interchange --
578 Representation of dates and times.
580 ISO/IEC 10646 (all parts), Information technology -- Universal Multiple-Octet Coded
581 Character Set (UCS).
585 <!--page 15 -->
589 For the purposes of this International Standard, the following definitions apply. Other
590 terms are defined where they appear in italic type or on the left side of a syntax rule.
591 Terms explicitly defined in this International Standard are not to be presumed to refer
592 implicitly to similar terms defined elsewhere. Terms not defined in this International
598 access
601 NOTE 1 Where only one of these two actions is meant, ''read'' or ''modify'' is used.
604 NOTE 2 "Modify'' includes the case where the new value being stored is the same as the previous value.
606 <p><!--para 4 -->
607 NOTE 3 Expressions that are not evaluated do not access objects.
611 <p><!--para 1 -->
612 alignment
613 requirement that objects of a particular type be located on storage boundaries with
614 addresses that are particular multiples of a byte address
617 <p><!--para 1 -->
618 argument
619 actual argument
620 actual parameter (deprecated)
621 expression in the comma-separated list bounded by the parentheses in a function call
622 expression, or a sequence of preprocessing tokens in the comma-separated list bounded
623 by the parentheses in a function-like macro invocation
626 <p><!--para 1 -->
627 behavior
628 external appearance or action
631 <p><!--para 1 -->
632 implementation-defined behavior
633 unspecified behavior where each implementation documents how the choice is made
634 <p><!--para 2 -->
635 EXAMPLE An example of implementation-defined behavior is the propagation of the high-order bit
636 when a signed integer is shifted right.
640 <p><!--para 1 -->
641 locale-specific behavior
642 behavior that depends on local conventions of nationality, culture, and language that each
643 implementation documents
644 <!--page 16 -->
645 <p><!--para 2 -->
646 EXAMPLE An example of locale-specific behavior is whether the islower function returns true for
647 characters other than the 26 lowercase Latin letters.
651 <p><!--para 1 -->
652 undefined behavior
653 behavior, upon use of a nonportable or erroneous program construct or of erroneous data,
654 for which this International Standard imposes no requirements
655 <p><!--para 2 -->
656 NOTE Possible undefined behavior ranges from ignoring the situation completely with unpredictable
657 results, to behaving during translation or program execution in a documented manner characteristic of the
658 environment (with or without the issuance of a diagnostic message), to terminating a translation or
659 execution (with the issuance of a diagnostic message).
661 <p><!--para 3 -->
662 EXAMPLE An example of undefined behavior is the behavior on integer overflow.
666 <p><!--para 1 -->
667 unspecified behavior
668 use of an unspecified value, or other behavior where this International Standard provides
669 two or more possibilities and imposes no further requirements on which is chosen in any
670 instance
671 <p><!--para 2 -->
672 EXAMPLE An example of unspecified behavior is the order in which the arguments to a function are
673 evaluated.
677 <p><!--para 1 -->
678 bit
679 unit of data storage in the execution environment large enough to hold an object that may
680 have one of two values
681 <p><!--para 2 -->
682 NOTE It need not be possible to express the address of each individual bit of an object.
686 <p><!--para 1 -->
687 byte
688 addressable unit of data storage large enough to hold any member of the basic character
689 set of the execution environment
690 <p><!--para 2 -->
691 NOTE 1 It is possible to express the address of each individual byte of an object uniquely.
693 <p><!--para 3 -->
694 NOTE 2 A byte is composed of a contiguous sequence of bits, the number of which is implementation-
695 defined. The least significant bit is called the low-order bit; the most significant bit is called the high-order
696 bit.
700 <p><!--para 1 -->
701 character
702 <abstract> member of a set of elements used for the organization, control, or
703 representation of data
706 <p><!--para 1 -->
707 character
708 single-byte character
709 <C> bit representation that fits in a byte
710 <!--page 17 -->
713 <p><!--para 1 -->
714 multibyte character
715 sequence of one or more bytes representing a member of the extended character set of
716 either the source or the execution environment
717 <p><!--para 2 -->
718 NOTE The extended character set is a superset of the basic character set.
722 <p><!--para 1 -->
723 wide character
724 bit representation that fits in an object of type wchar_t, capable of representing any
725 character in the current locale
728 <p><!--para 1 -->
729 constraint
730 restriction, either syntactic or semantic, by which the exposition of language elements is
731 to be interpreted
734 <p><!--para 1 -->
735 correctly rounded result
736 representation in the result format that is nearest in value, subject to the current rounding
737 mode, to what the result would be given unlimited range and precision
740 <p><!--para 1 -->
741 diagnostic message
742 message belonging to an implementation-defined subset of the implementation's message
743 output
746 <p><!--para 1 -->
747 forward reference
748 reference to a later subclause of this International Standard that contains additional
749 information relevant to this subclause
752 <p><!--para 1 -->
753 implementation
754 particular set of software, running in a particular translation environment under particular
755 control options, that performs translation of programs for, and supports execution of
756 functions in, a particular execution environment
759 <p><!--para 1 -->
760 implementation limit
761 restriction imposed upon programs by the implementation
764 <p><!--para 1 -->
765 object
766 region of data storage in the execution environment, the contents of which can represent
767 values
768 <!--page 18 -->
769 <p><!--para 2 -->
770 NOTE When referenced, an object may be interpreted as having a particular type; see <a href="#6.3.2.1">6.3.2.1</a>.
774 <p><!--para 1 -->
775 parameter
776 formal parameter
777 formal argument (deprecated)
778 object declared as part of a function declaration or definition that acquires a value on
779 entry to the function, or an identifier from the comma-separated list bounded by the
780 parentheses immediately following the macro name in a function-like macro definition
783 <p><!--para 1 -->
784 recommended practice
785 specification that is strongly recommended as being in keeping with the intent of the
786 standard, but that may be impractical for some implementations
789 <p><!--para 1 -->
790 value
791 precise meaning of the contents of an object when interpreted as having a specific type
794 <p><!--para 1 -->
795 implementation-defined value
796 unspecified value where each implementation documents how the choice is made
799 <p><!--para 1 -->
800 indeterminate value
801 either an unspecified value or a trap representation
804 <p><!--para 1 -->
805 unspecified value
806 valid value of the relevant type where this International Standard imposes no
807 requirements on which value is chosen in any instance
808 <p><!--para 2 -->
809 NOTE An unspecified value cannot be a trap representation.
813 <p><!--para 1 -->
814 ??? x???
815 ceiling of x: the least integer greater than or equal to x
816 <p><!--para 2 -->
817 EXAMPLE ???2.4??? is 3, ???-2.4??? is -2.
821 <p><!--para 1 -->
822 ??? x???
823 floor of x: the greatest integer less than or equal to x
824 <p><!--para 2 -->
825 EXAMPLE ???2.4??? is 2, ???-2.4??? is -3.
826 <!--page 19 -->
829 <p><!--para 1 -->
830 In this International Standard, ''shall'' is to be interpreted as a requirement on an
831 implementation or on a program; conversely, ''shall not'' is to be interpreted as a
832 prohibition.
833 <p><!--para 2 -->
834 If a ''shall'' or ''shall not'' requirement that appears outside of a constraint is violated, the
835 behavior is undefined. Undefined behavior is otherwise indicated in this International
836 Standard by the words ''undefined behavior'' or by the omission of any explicit definition
837 of behavior. There is no difference in emphasis among these three; they all describe
838 ''behavior that is undefined''.
839 <p><!--para 3 -->
840 A program that is correct in all other aspects, operating on correct data, containing
841 unspecified behavior shall be a correct program and act in accordance with <a href="#5.1.2.3">5.1.2.3</a>.
842 <p><!--para 4 -->
843 The implementation shall not successfully translate a preprocessing translation unit
844 containing a #error preprocessing directive unless it is part of a group skipped by
845 conditional inclusion.
846 <p><!--para 5 -->
847 A strictly conforming program shall use only those features of the language and library
848 specified in this International Standard.<sup><a href="#note2"><b>2)</b></a></sup> It shall not produce output dependent on any
849 unspecified, undefined, or implementation-defined behavior, and shall not exceed any
850 minimum implementation limit.
851 <p><!--para 6 -->
852 The two forms of conforming implementation are hosted and freestanding. A conforming
853 hosted implementation shall accept any strictly conforming program. A conforming
854 freestanding implementation shall accept any strictly conforming program that does not
855 use complex types and in which the use of the features specified in the library clause
856 (clause 7) is confined to the contents of the standard headers <a href="#7.7"><float.h></a>,
857 <a href="#7.9"><iso646.h></a>, <a href="#7.10"><limits.h></a>, <a href="#7.15"><stdarg.h></a>, <a href="#7.16"><stdbool.h></a>, <a href="#7.17"><stddef.h></a>, and
858 <a href="#7.18"><stdint.h></a>. A conforming implementation may have extensions (including additional
859 library functions), provided they do not alter the behavior of any strictly conforming
864 <!--page 20 -->
865 <p><!--para 7 -->
866 A conforming program is one that is acceptable to a conforming implementation.<sup><a href="#note4"><b>4)</b></a></sup>
867 <p><!--para 8 -->
868 An implementation shall be accompanied by a document that defines all implementation-
869 defined and locale-specific characteristics and all extensions.
870 <p><b> Forward references</b>: conditional inclusion (<a href="#6.10.1">6.10.1</a>), error directive (<a href="#6.10.5">6.10.5</a>),
871 characteristics of floating types <a href="#7.7"><float.h></a> (<a href="#7.7">7.7</a>), alternative spellings <a href="#7.9"><iso646.h></a>
872 (<a href="#7.9">7.9</a>), sizes of integer types <a href="#7.10"><limits.h></a> (<a href="#7.10">7.10</a>), variable arguments <a href="#7.15"><stdarg.h></a>
873 (<a href="#7.15">7.15</a>), boolean type and values <a href="#7.16"><stdbool.h></a> (<a href="#7.16">7.16</a>), common definitions
874 <a href="#7.17"><stddef.h></a> (<a href="#7.17">7.17</a>), integer types <a href="#7.18"><stdint.h></a> (<a href="#7.18">7.18</a>).
879 <!--page 21 -->
881 <h6>footnotes</h6>
882 <p><small><a name="note2" href="#note2">2)</a> A strictly conforming program can use conditional features (such as those in <a href="#F">annex F</a>) provided the
883 use is guarded by a #ifdef directive with the appropriate macro. For example:
885 <pre>
886 #ifdef __STDC_IEC_559__ /* FE_UPWARD defined */
887 /* ... */
888 fesetround(FE_UPWARD);
889 /* ... */
890 #endif</pre>
892 </small>
893 <p><small><a name="note3" href="#note3">3)</a> This implies that a conforming implementation reserves no identifiers other than those explicitly
894 reserved in this International Standard.
895 </small>
896 <p><small><a name="note4" href="#note4">4)</a> Strictly conforming programs are intended to be maximally portable among conforming
897 implementations. Conforming programs may depend upon nonportable features of a conforming
898 implementation.
899 </small>
902 <p><!--para 1 -->
903 An implementation translates C source files and executes C programs in two data-
904 processing-system environments, which will be called the translation environment and
905 the execution environment in this International Standard. Their characteristics define and
906 constrain the results of executing conforming C programs constructed according to the
907 syntactic and semantic rules for conforming implementations.
908 <p><b> Forward references</b>: In this clause, only a few of many possible forward references
909 have been noted.
916 <p><!--para 1 -->
917 A C program need not all be translated at the same time. The text of the program is kept
918 in units called source files, (or preprocessing files) in this International Standard. A
919 source file together with all the headers and source files included via the preprocessing
920 directive #include is known as a preprocessing translation unit. After preprocessing, a
921 preprocessing translation unit is called a translation unit. Previously translated translation
922 units may be preserved individually or in libraries. The separate translation units of a
923 program communicate by (for example) calls to functions whose identifiers have external
924 linkage, manipulation of objects whose identifiers have external linkage, or manipulation
925 of data files. Translation units may be separately translated and then later linked to
926 produce an executable program.
927 <p><b> Forward references</b>: linkages of identifiers (<a href="#6.2.2">6.2.2</a>), external definitions (<a href="#6.9">6.9</a>),
931 <p><!--para 1 -->
932 The precedence among the syntax rules of translation is specified by the following
934 <ol>
935 <li> Physical source file multibyte characters are mapped, in an implementation-
936 defined manner, to the source character set (introducing new-line characters for
937 end-of-line indicators) if necessary. Trigraph sequences are replaced by
938 corresponding single-character internal representations.
942 <!--page 22 -->
943 <li> Each instance of a backslash character (\) immediately followed by a new-line
944 character is deleted, splicing physical source lines to form logical source lines.
945 Only the last backslash on any physical source line shall be eligible for being part
946 of such a splice. A source file that is not empty shall end in a new-line character,
947 which shall not be immediately preceded by a backslash character before any such
948 splicing takes place.
949 <li> The source file is decomposed into preprocessing tokens<sup><a href="#note6"><b>6)</b></a></sup> and sequences of
950 white-space characters (including comments). A source file shall not end in a
951 partial preprocessing token or in a partial comment. Each comment is replaced by
952 one space character. New-line characters are retained. Whether each nonempty
953 sequence of white-space characters other than new-line is retained or replaced by
954 one space character is implementation-defined.
955 <li> Preprocessing directives are executed, macro invocations are expanded, and
956 _Pragma unary operator expressions are executed. If a character sequence that
957 matches the syntax of a universal character name is produced by token
958 concatenation (<a href="#6.10.3.3">6.10.3.3</a>), the behavior is undefined. A #include preprocessing
959 directive causes the named header or source file to be processed from phase 1
960 through phase 4, recursively. All preprocessing directives are then deleted.
961 <li> Each source character set member and escape sequence in character constants and
962 string literals is converted to the corresponding member of the execution character
963 set; if there is no corresponding member, it is converted to an implementation-
965 <li> Adjacent string literal tokens are concatenated.
966 <li> White-space characters separating tokens are no longer significant. Each
967 preprocessing token is converted into a token. The resulting tokens are
968 syntactically and semantically analyzed and translated as a translation unit.
969 <li> All external object and function references are resolved. Library components are
970 linked to satisfy external references to functions and objects not defined in the
971 current translation. All such translator output is collected into a program image
972 which contains information needed for execution in its execution environment.
973 </ol>
974 <p><b> Forward references</b>: universal character names (<a href="#6.4.3">6.4.3</a>), lexical elements (<a href="#6.4">6.4</a>),
975 preprocessing directives (<a href="#6.10">6.10</a>), trigraph sequences (<a href="#5.2.1.1">5.2.1.1</a>), external definitions (<a href="#6.9">6.9</a>).
979 <!--page 23 -->
981 <h6>footnotes</h6>
982 <p><small><a name="note5" href="#note5">5)</a> Implementations shall behave as if these separate phases occur, even though many are typically folded
983 together in practice. Source files, translation units, and translated translation units need not
984 necessarily be stored as files, nor need there be any one-to-one correspondence between these entities
985 and any external representation. The description is conceptual only, and does not specify any
986 particular implementation.
987 </small>
988 <p><small><a name="note6" href="#note6">6)</a> As described in <a href="#6.4">6.4</a>, the process of dividing a source file's characters into preprocessing tokens is
989 context-dependent. For example, see the handling of < within a #include preprocessing directive.
990 </small>
991 <p><small><a name="note7" href="#note7">7)</a> An implementation need not convert all non-corresponding source characters to the same execution
992 character.
993 </small>
996 <p><!--para 1 -->
997 A conforming implementation shall produce at least one diagnostic message (identified in
998 an implementation-defined manner) if a preprocessing translation unit or translation unit
999 contains a violation of any syntax rule or constraint, even if the behavior is also explicitly
1000 specified as undefined or implementation-defined. Diagnostic messages need not be
1002 <p><!--para 2 -->
1003 EXAMPLE An implementation shall issue a diagnostic for the translation unit:
1004 <pre>
1005 char i;
1006 int i;</pre>
1007 because in those cases where wording in this International Standard describes the behavior for a construct
1008 as being both a constraint error and resulting in undefined behavior, the constraint error shall be diagnosed.
1011 <h6>footnotes</h6>
1012 <p><small><a name="note8" href="#note8">8)</a> The intent is that an implementation should identify the nature of, and where possible localize, each
1013 violation. Of course, an implementation is free to produce any number of diagnostics as long as a
1014 valid program is still correctly translated. It may also successfully translate an invalid program.
1015 </small>
1018 <p><!--para 1 -->
1019 Two execution environments are defined: freestanding and hosted. In both cases,
1020 program startup occurs when a designated C function is called by the execution
1021 environment. All objects with static storage duration shall be initialized (set to their
1022 initial values) before program startup. The manner and timing of such initialization are
1023 otherwise unspecified. Program termination returns control to the execution
1024 environment.
1025 <p><b> Forward references</b>: storage durations of objects (<a href="#6.2.4">6.2.4</a>), initialization (<a href="#6.7.8">6.7.8</a>).
1028 <p><!--para 1 -->
1029 In a freestanding environment (in which C program execution may take place without any
1030 benefit of an operating system), the name and type of the function called at program
1031 startup are implementation-defined. Any library facilities available to a freestanding
1032 program, other than the minimal set required by clause 4, are implementation-defined.
1033 <p><!--para 2 -->
1034 The effect of program termination in a freestanding environment is implementation-
1035 defined.
1038 <p><!--para 1 -->
1039 A hosted environment need not be provided, but shall conform to the following
1040 specifications if present.
1045 <!--page 24 -->
1048 <p><!--para 1 -->
1049 The function called at program startup is named main. The implementation declares no
1050 prototype for this function. It shall be defined with a return type of int and with no
1051 parameters:
1052 <pre>
1053 int main(void) { /* ... */ }</pre>
1054 or with two parameters (referred to here as argc and argv, though any names may be
1055 used, as they are local to the function in which they are declared):
1056 <pre>
1057 int main(int argc, char *argv[]) { /* ... */ }</pre>
1058 or equivalent;<sup><a href="#note9"><b>9)</b></a></sup> or in some other implementation-defined manner.
1059 <p><!--para 2 -->
1060 If they are declared, the parameters to the main function shall obey the following
1061 constraints:
1062 <ul>
1063 <li> The value of argc shall be nonnegative.
1064 <li> argv[argc] shall be a null pointer.
1065 <li> If the value of argc is greater than zero, the array members argv[0] through
1066 argv[argc-1] inclusive shall contain pointers to strings, which are given
1067 implementation-defined values by the host environment prior to program startup. The
1068 intent is to supply to the program information determined prior to program startup
1069 from elsewhere in the hosted environment. If the host environment is not capable of
1070 supplying strings with letters in both uppercase and lowercase, the implementation
1071 shall ensure that the strings are received in lowercase.
1072 <li> If the value of argc is greater than zero, the string pointed to by argv[0]
1073 represents the program name; argv[0][0] shall be the null character if the
1074 program name is not available from the host environment. If the value of argc is
1075 greater than one, the strings pointed to by argv[1] through argv[argc-1]
1076 represent the program parameters.
1077 <li> The parameters argc and argv and the strings pointed to by the argv array shall
1078 be modifiable by the program, and retain their last-stored values between program
1079 startup and program termination.
1080 </ul>
1082 <h6>footnotes</h6>
1083 <p><small><a name="note9" href="#note9">9)</a> Thus, int can be replaced by a typedef name defined as int, or the type of argv can be written as
1084 char ** argv, and so on.
1085 </small>
1088 <p><!--para 1 -->
1089 In a hosted environment, a program may use all the functions, macros, type definitions,
1090 and objects described in the library clause (clause 7).
1094 <!--page 25 -->
1097 <p><!--para 1 -->
1098 If the return type of the main function is a type compatible with int, a return from the
1099 initial call to the main function is equivalent to calling the exit function with the value
1100 returned by the main function as its argument;<sup><a href="#note10"><b>10)</b></a></sup> reaching the } that terminates the
1101 main function returns a value of 0. If the return type is not compatible with int, the
1102 termination status returned to the host environment is unspecified.
1103 <p><b> Forward references</b>: definition of terms (<a href="#7.1.1">7.1.1</a>), the exit function (<a href="#7.20.4.3">7.20.4.3</a>).
1105 <h6>footnotes</h6>
1106 <p><small><a name="note10" href="#note10">10)</a> In accordance with <a href="#6.2.4">6.2.4</a>, the lifetimes of objects with automatic storage duration declared in main
1107 will have ended in the former case, even where they would not have in the latter.
1108 </small>
1111 <p><!--para 1 -->
1112 The semantic descriptions in this International Standard describe the behavior of an
1113 abstract machine in which issues of optimization are irrelevant.
1114 <p><!--para 2 -->
1115 Accessing a volatile object, modifying an object, modifying a file, or calling a function
1116 that does any of those operations are all side effects,<sup><a href="#note11"><b>11)</b></a></sup> which are changes in the state of
1117 the execution environment. Evaluation of an expression may produce side effects. At
1118 certain specified points in the execution sequence called sequence points, all side effects
1119 of previous evaluations shall be complete and no side effects of subsequent evaluations
1120 shall have taken place. (A summary of the sequence points is given in <a href="#C">annex C</a>.)
1121 <p><!--para 3 -->
1122 In the abstract machine, all expressions are evaluated as specified by the semantics. An
1123 actual implementation need not evaluate part of an expression if it can deduce that its
1124 value is not used and that no needed side effects are produced (including any caused by
1125 calling a function or accessing a volatile object).
1126 <p><!--para 4 -->
1127 When the processing of the abstract machine is interrupted by receipt of a signal, only the
1128 values of objects as of the previous sequence point may be relied on. Objects that may be
1129 modified between the previous sequence point and the next sequence point need not have
1130 received their correct values yet.
1131 <p><!--para 5 -->
1132 The least requirements on a conforming implementation are:
1133 <ul>
1134 <li> At sequence points, volatile objects are stable in the sense that previous accesses are
1135 complete and subsequent accesses have not yet occurred.
1140 <!--page 26 -->
1141 <li> At program termination, all data written into files shall be identical to the result that
1142 execution of the program according to the abstract semantics would have produced.
1143 <li> The input and output dynamics of interactive devices shall take place as specified in
1144 <a href="#7.19.3">7.19.3</a>. The intent of these requirements is that unbuffered or line-buffered output
1145 appear as soon as possible, to ensure that prompting messages actually appear prior to
1146 a program waiting for input.
1147 </ul>
1148 <p><!--para 6 -->
1149 What constitutes an interactive device is implementation-defined.
1150 <p><!--para 7 -->
1151 More stringent correspondences between abstract and actual semantics may be defined by
1152 each implementation.
1153 <p><!--para 8 -->
1154 EXAMPLE 1 An implementation might define a one-to-one correspondence between abstract and actual
1155 semantics: at every sequence point, the values of the actual objects would agree with those specified by the
1156 abstract semantics. The keyword volatile would then be redundant.
1157 <p><!--para 9 -->
1158 Alternatively, an implementation might perform various optimizations within each translation unit, such
1159 that the actual semantics would agree with the abstract semantics only when making function calls across
1160 translation unit boundaries. In such an implementation, at the time of each function entry and function
1161 return where the calling function and the called function are in different translation units, the values of all
1162 externally linked objects and of all objects accessible via pointers therein would agree with the abstract
1163 semantics. Furthermore, at the time of each such function entry the values of the parameters of the called
1164 function and of all objects accessible via pointers therein would agree with the abstract semantics. In this
1165 type of implementation, objects referred to by interrupt service routines activated by the signal function
1166 would require explicit specification of volatile storage, as well as other implementation-defined
1167 restrictions.
1169 <p><!--para 10 -->
1170 EXAMPLE 2 In executing the fragment
1171 <pre>
1172 char c1, c2;
1173 /* ... */
1174 c1 = c1 + c2;</pre>
1175 the ''integer promotions'' require that the abstract machine promote the value of each variable to int size
1176 and then add the two ints and truncate the sum. Provided the addition of two chars can be done without
1177 overflow, or with overflow wrapping silently to produce the correct result, the actual execution need only
1178 produce the same result, possibly omitting the promotions.
1180 <p><!--para 11 -->
1181 EXAMPLE 3 Similarly, in the fragment
1182 <pre>
1183 float f1, f2;
1184 double d;
1185 /* ... */
1186 f1 = f2 * d;</pre>
1187 the multiplication may be executed using single-precision arithmetic if the implementation can ascertain
1188 that the result would be the same as if it were executed using double-precision arithmetic (for example, if d
1189 were replaced by the constant 2.0, which has type double).
1190 <!--page 27 -->
1191 <p><!--para 12 -->
1192 EXAMPLE 4 Implementations employing wide registers have to take care to honor appropriate
1193 semantics. Values are independent of whether they are represented in a register or in memory. For
1194 example, an implicit spilling of a register is not permitted to alter the value. Also, an explicit store and load
1195 is required to round to the precision of the storage type. In particular, casts and assignments are required to
1196 perform their specified conversion. For the fragment
1197 <pre>
1198 double d1, d2;
1199 float f;
1200 d1 = f = expression;
1201 d2 = (float) expression;</pre>
1202 the values assigned to d1 and d2 are required to have been converted to float.
1204 <p><!--para 13 -->
1205 EXAMPLE 5 Rearrangement for floating-point expressions is often restricted because of limitations in
1206 precision as well as range. The implementation cannot generally apply the mathematical associative rules
1207 for addition or multiplication, nor the distributive rule, because of roundoff error, even in the absence of
1208 overflow and underflow. Likewise, implementations cannot generally replace decimal constants in order to
1209 rearrange expressions. In the following fragment, rearrangements suggested by mathematical rules for real
1211 <pre>
1212 double x, y, z;
1213 /* ... */
1214 x = (x * y) * z; // not equivalent to x *= y * z;
1215 z = (x - y) + y ; // not equivalent to z = x;
1216 z = x + x * y; // not equivalent to z = x * (1.0 + y);
1217 y = x / 5.0; // not equivalent to y = x * 0.2;</pre>
1219 <p><!--para 14 -->
1220 EXAMPLE 6 To illustrate the grouping behavior of expressions, in the following fragment
1221 <pre>
1222 int a, b;
1223 /* ... */
1224 a = a + 32760 + b + 5;</pre>
1225 the expression statement behaves exactly the same as
1226 <pre>
1227 a = (((a + 32760) + b) + 5);</pre>
1228 due to the associativity and precedence of these operators. Thus, the result of the sum (a + 32760) is
1229 next added to b, and that result is then added to 5 which results in the value assigned to a. On a machine in
1230 which overflows produce an explicit trap and in which the range of values representable by an int is
1231 [-32768, +32767], the implementation cannot rewrite this expression as
1232 <pre>
1233 a = ((a + b) + 32765);</pre>
1234 since if the values for a and b were, respectively, -32754 and -15, the sum a + b would produce a trap
1235 while the original expression would not; nor can the expression be rewritten either as
1236 <pre>
1237 a = ((a + 32765) + b);</pre>
1238 or
1239 <pre>
1240 a = (a + (b + 32765));</pre>
1241 since the values for a and b might have been, respectively, 4 and -8 or -17 and 12. However, on a machine
1242 in which overflow silently generates some value and where positive and negative overflows cancel, the
1243 above expression statement can be rewritten by the implementation in any of the above ways because the
1244 same result will occur.
1245 <!--page 28 -->
1246 <p><!--para 15 -->
1247 EXAMPLE 7 The grouping of an expression does not completely determine its evaluation. In the
1248 following fragment
1249 <pre>
1251 int sum;
1252 char *p;
1253 /* ... */
1254 sum = sum * 10 - '0' + (*p++ = getchar());</pre>
1255 the expression statement is grouped as if it were written as
1256 <pre>
1257 sum = (((sum * 10) - '0') + ((*(p++)) = (getchar())));</pre>
1258 but the actual increment of p can occur at any time between the previous sequence point and the next
1259 sequence point (the ;), and the call to getchar can occur at any point prior to the need of its returned
1260 value.
1262 <p><b> Forward references</b>: expressions (<a href="#6.5">6.5</a>), type qualifiers (<a href="#6.7.3">6.7.3</a>), statements (<a href="#6.8">6.8</a>), the
1264 <!--page 29 -->
1266 <h6>footnotes</h6>
1267 <p><small><a name="note11" href="#note11">11)</a> The IEC 60559 standard for binary floating-point arithmetic requires certain user-accessible status
1268 flags and control modes. Floating-point operations implicitly set the status flags; modes affect result
1269 values of floating-point operations. Implementations that support such floating-point state are
1270 required to regard changes to it as side effects -- see <a href="#F">annex F</a> for details. The floating-point
1271 environment library <a href="#7.6"><fenv.h></a> provides a programming facility for indicating when these side
1272 effects matter, freeing the implementations in other cases.
1273 </small>
1278 <p><!--para 1 -->
1279 Two sets of characters and their associated collating sequences shall be defined: the set in
1280 which source files are written (the source character set), and the set interpreted in the
1281 execution environment (the execution character set). Each set is further divided into a
1282 basic character set, whose contents are given by this subclause, and a set of zero or more
1283 locale-specific members (which are not members of the basic character set) called
1284 extended characters. The combined set is also called the extended character set. The
1285 values of the members of the execution character set are implementation-defined.
1286 <p><!--para 2 -->
1287 In a character constant or string literal, members of the execution character set shall be
1288 represented by corresponding members of the source character set or by escape
1289 sequences consisting of the backslash \ followed by one or more characters. A byte with
1290 all bits set to 0, called the null character, shall exist in the basic execution character set; it
1291 is used to terminate a character string.
1292 <p><!--para 3 -->
1293 Both the basic source and basic execution character sets shall have the following
1294 members: the 26 uppercase letters of the Latin alphabet
1295 <pre>
1296 A B C D E F G H I J K L M
1297 N O P Q R S T U V W X Y Z</pre>
1298 the 26 lowercase letters of the Latin alphabet
1299 <pre>
1300 a b c d e f g h i j k l m
1301 n o p q r s t u v w x y z</pre>
1302 the 10 decimal digits
1303 <pre>
1304 0 1 2 3 4 5 6 7 8 9</pre>
1305 the following 29 graphic characters
1306 <pre>
1309 the space character, and control characters representing horizontal tab, vertical tab, and
1310 form feed. The representation of each member of the source and execution basic
1311 character sets shall fit in a byte. In both the source and execution basic character sets, the
1312 value of each character after 0 in the above list of decimal digits shall be one greater than
1313 the value of the previous. In source files, there shall be some way of indicating the end of
1314 each line of text; this International Standard treats such an end-of-line indicator as if it
1315 were a single new-line character. In the basic execution character set, there shall be
1316 control characters representing alert, backspace, carriage return, and new line. If any
1317 other characters are encountered in a source file (except in an identifier, a character
1318 constant, a string literal, a header name, a comment, or a preprocessing token that is never
1319 <!--page 30 -->
1320 converted to a token), the behavior is undefined.
1322 A letter is an uppercase letter or a lowercase letter as defined above; in this International
1323 Standard the term does not include other characters that are letters in other alphabets.
1325 The universal character name construct provides a way to name other characters.
1326 <p><b> Forward references</b>: universal character names (<a href="#6.4.3">6.4.3</a>), character constants (<a href="#6.4.4.4">6.4.4.4</a>),
1327 preprocessing directives (<a href="#6.10">6.10</a>), string literals (<a href="#6.4.5">6.4.5</a>), comments (<a href="#6.4.9">6.4.9</a>), string (<a href="#7.1.1">7.1.1</a>).
1331 Before any other processing takes place, each occurrence of one of the following
1332 sequences of three characters (called trigraph sequences<sup><a href="#note12"><b>12)</b></a></sup>) is replaced with the
1333 corresponding single character.
1334 <pre>
1335 ??= # ??) ] ??! |
1336 ??( [ ??' ^ ??> }
1338 No other trigraph sequences exist. Each ? that does not begin one of the trigraphs listed
1339 above is not changed.
1341 EXAMPLE 1
1342 <pre>
1343 ??=define arraycheck(a, b) a??(b??) ??!??! b??(a??)</pre>
1344 becomes
1345 <pre>
1346 #define arraycheck(a, b) a[b] || b[a]</pre>
1349 EXAMPLE 2 The following source line
1350 <pre>
1352 becomes (after replacement of the trigraph sequence ??/)
1353 <pre>
1358 <p><small><a name="note12" href="#note12">12)</a> The trigraph sequences enable the input of characters that are not defined in the Invariant Code Set as
1359 described in ISO/IEC 646, which is a subset of the seven-bit US ASCII code set.
1360 </small>
1364 The source character set may contain multibyte characters, used to represent members of
1365 the extended character set. The execution character set may also contain multibyte
1366 characters, which need not have the same encoding as for the source character set. For
1367 both character sets, the following shall hold:
1368 <ul>
1369 <li> The basic character set shall be present and each character shall be encoded as a
1370 single byte.
1371 <li> The presence, meaning, and representation of any additional members is locale-
1372 specific.
1374 <!--page 31 -->
1375 <li> A multibyte character set may have a state-dependent encoding, wherein each
1376 sequence of multibyte characters begins in an initial shift state and enters other
1377 locale-specific shift states when specific multibyte characters are encountered in the
1378 sequence. While in the initial shift state, all single-byte characters retain their usual
1379 interpretation and do not alter the shift state. The interpretation for subsequent bytes
1380 in the sequence is a function of the current shift state.
1381 <li> A byte with all bits zero shall be interpreted as a null character independent of shift
1382 state. Such a byte shall not occur as part of any other multibyte character.
1383 </ul>
1385 For source files, the following shall hold:
1386 <ul>
1387 <li> An identifier, comment, string literal, character constant, or header name shall begin
1388 and end in the initial shift state.
1389 <li> An identifier, comment, string literal, character constant, or header name shall consist
1390 of a sequence of valid multibyte characters.
1391 </ul>
1395 The active position is that location on a display device where the next character output by
1396 the fputc function would appear. The intent of writing a printing character (as defined
1397 by the isprint function) to a display device is to display a graphic representation of
1398 that character at the active position and then advance the active position to the next
1399 position on the current line. The direction of writing is locale-specific. If the active
1400 position is at the final position of a line (if there is one), the behavior of the display device
1401 is unspecified.
1403 Alphabetic escape sequences representing nongraphic characters in the execution
1404 character set are intended to produce actions on display devices as follows:
1405 \a (alert) Produces an audible or visible alert without changing the active position.
1406 \b (backspace) Moves the active position to the previous position on the current line. If
1407 <pre>
1408 the active position is at the initial position of a line, the behavior of the display
1409 device is unspecified.</pre>
1410 \f ( form feed) Moves the active position to the initial position at the start of the next
1411 <pre>
1412 logical page.</pre>
1413 \n (new line) Moves the active position to the initial position of the next line.
1414 \r (carriage return) Moves the active position to the initial position of the current line.
1415 \t (horizontal tab) Moves the active position to the next horizontal tabulation position
1416 <pre>
1417 on the current line. If the active position is at or past the last defined horizontal
1418 tabulation position, the behavior of the display device is unspecified.</pre>
1419 \v (vertical tab) Moves the active position to the initial position of the next vertical
1420 <!--page 32 -->
1422 <pre>
1423 tabulation position. If the active position is at or past the last defined vertical
1424 tabulation position, the behavior of the display device is unspecified.</pre>
1425 Each of these escape sequences shall produce a unique implementation-defined value
1426 which can be stored in a single char object. The external representations in a text file
1427 need not be identical to the internal representations, and are outside the scope of this
1428 International Standard.
1429 <p><b> Forward references</b>: the isprint function (<a href="#7.4.1.8">7.4.1.8</a>), the fputc function (<a href="#7.19.7.3">7.19.7.3</a>).
1433 Functions shall be implemented such that they may be interrupted at any time by a signal,
1434 or may be called by a signal handler, or both, with no alteration to earlier, but still active,
1435 invocations' control flow (after the interruption), function return values, or objects with
1436 automatic storage duration. All such objects shall be maintained outside the function
1437 image (the instructions that compose the executable representation of a function) on a
1438 per-invocation basis.
1442 Both the translation and execution environments constrain the implementation of
1443 language translators and libraries. The following summarizes the language-related
1444 environmental limits on a conforming implementation; the library-related limits are
1445 discussed in clause 7.
1449 The implementation shall be able to translate and execute at least one program that
1450 contains at least one instance of every one of the following limits:<sup><a href="#note13"><b>13)</b></a></sup>
1451 <ul>
1455 arithmetic, structure, union, or incomplete type in a declaration
1459 universal character name or extended source character is considered a single
1460 character)
1461 <li> 31 significant initial characters in an external identifier (each universal character name
1465 <!--page 33 -->
1466 universal character name specifying a short identifier of 00010000 or more is
1467 considered 10 characters, and each extended source character is considered the same
1468 number of characters as the corresponding universal character name, if any)<sup><a href="#note14"><b>14)</b></a></sup>
1477 <li> 4095 characters in a character string literal or wide string literal (after concatenation)
1481 statements)
1485 </ul>
1488 <p><small><a name="note13" href="#note13">13)</a> Implementations should avoid imposing fixed translation limits whenever possible.
1489 </small>
1490 <p><small><a name="note14" href="#note14">14)</a> See ''future language directions'' (<a href="#6.11.3">6.11.3</a>).
1491 </small>
1495 An implementation is required to document all the limits specified in this subclause,
1496 which are specified in the headers <a href="#7.10"><limits.h></a> and <a href="#7.7"><float.h></a>. Additional limits are
1498 <p><b> Forward references</b>: integer types <a href="#7.18"><stdint.h></a> (<a href="#7.18">7.18</a>).
1502 The values given below shall be replaced by constant expressions suitable for use in #if
1503 preprocessing directives. Moreover, except for CHAR_BIT and MB_LEN_MAX, the
1504 following shall be replaced by expressions that have the same type as would an
1505 expression that is an object of the corresponding type converted according to the integer
1506 promotions. Their implementation-defined values shall be equal or greater in magnitude
1509 <!--page 34 -->
1510 (absolute value) to those shown, with the same sign.
1511 <ul>
1512 <li> number of bits for smallest object that is not a bit-field (byte)
1513 CHAR_BIT 8
1514 <li> minimum value for an object of type signed char
1516 <li> maximum value for an object of type signed char
1518 <li> maximum value for an object of type unsigned char
1520 <li> minimum value for an object of type char
1521 CHAR_MIN see below
1522 <li> maximum value for an object of type char
1523 CHAR_MAX see below
1524 <li> maximum number of bytes in a multibyte character, for any supported locale
1525 MB_LEN_MAX 1
1526 <li> minimum value for an object of type short int
1528 <li> maximum value for an object of type short int
1530 <li> maximum value for an object of type unsigned short int
1532 <li> minimum value for an object of type int
1534 <li> maximum value for an object of type int
1536 <li> maximum value for an object of type unsigned int
1538 <li> minimum value for an object of type long int
1540 <li> maximum value for an object of type long int
1542 <li> maximum value for an object of type unsigned long int
1544 <!--page 35 -->
1545 <li> minimum value for an object of type long long int
1547 <li> maximum value for an object of type long long int
1549 <li> maximum value for an object of type unsigned long long int
1551 </ul>
1553 If the value of an object of type char is treated as a signed integer when used in an
1554 expression, the value of CHAR_MIN shall be the same as that of SCHAR_MIN and the
1555 value of CHAR_MAX shall be the same as that of SCHAR_MAX. Otherwise, the value of
1556 CHAR_MIN shall be 0 and the value of CHAR_MAX shall be the same as that of
1557 UCHAR_MAX.<sup><a href="#note15"><b>15)</b></a></sup> The value UCHAR_MAX shall equal 2CHAR_BIT - 1.
1558 <p><b> Forward references</b>: representations of types (<a href="#6.2.6">6.2.6</a>), conditional inclusion (<a href="#6.10.1">6.10.1</a>).
1562 </small>
1564 <h5><a name="5.2.4.2.2" href="#5.2.4.2.2">5.2.4.2.2 Characteristics of floating types <float.h></a></h5>
1566 The characteristics of floating types are defined in terms of a model that describes a
1567 representation of floating-point numbers and values that provide information about an
1568 implementation's floating-point arithmetic.<sup><a href="#note16"><b>16)</b></a></sup> The following parameters are used to
1569 define the model for each floating-point type:
1571 <pre>
1572 s sign ((+-)1)
1574 e exponent (an integer between a minimum emin and a maximum emax )
1575 p precision (the number of base-b digits in the significand)
1576 fk nonnegative integers less than b (the significand digits)</pre>
1577 A floating-point number (x) is defined by the following model:
1578 <pre>
1579 p
1580 x = sb e (Sum) f k b-k ,
1581 k=1
1585 In addition to normalized floating-point numbers ( f 1 > 0 if x != 0), floating types may be
1586 able to contain other kinds of floating-point numbers, such as subnormal floating-point
1589 NaNs. A NaN is an encoding signifying Not-a-Number. A quiet NaN propagates
1590 through almost every arithmetic operation without raising a floating-point exception; a
1591 signaling NaN generally raises a floating-point exception when occurring as an
1594 <!--page 36 -->
1597 An implementation may give zero and non-numeric values (such as infinities and NaNs) a
1598 sign or may leave them unsigned. Wherever such values are unsigned, any requirement
1599 in this International Standard to retrieve the sign shall produce an unspecified sign, and
1600 any requirement to set the sign shall be ignored.
1602 The accuracy of the floating-point operations (+, -, *, /) and of the library functions in
1603 <a href="#7.12"><math.h></a> and <a href="#7.3"><complex.h></a> that return floating-point results is implementation-
1604 defined, as is the accuracy of the conversion between floating-point internal
1605 representations and string representations performed by the library functions in
1606 <a href="#7.19"><stdio.h></a>, <a href="#7.20"><stdlib.h></a>, and <a href="#7.24"><wchar.h></a>. The implementation may state that the
1607 accuracy is unknown.
1609 All integer values in the <a href="#7.7"><float.h></a> header, except FLT_ROUNDS, shall be constant
1610 expressions suitable for use in #if preprocessing directives; all floating values shall be
1611 constant expressions. All except DECIMAL_DIG, FLT_EVAL_METHOD, FLT_RADIX,
1612 and FLT_ROUNDS have separate names for all three floating-point types. The floating-
1613 point model representation is provided for all values except FLT_EVAL_METHOD and
1614 FLT_ROUNDS.
1616 The rounding mode for floating-point addition is characterized by the implementation-
1618 <pre>
1619 -1 indeterminable
1620 0 toward zero
1621 1 to nearest
1622 2 toward positive infinity
1624 All other values for FLT_ROUNDS characterize implementation-defined rounding
1625 behavior.
1627 Except for assignment and cast (which remove all extra range and precision), the values
1628 of operations with floating operands and values subject to the usual arithmetic
1629 conversions and of floating constants are evaluated to a format whose range and precision
1630 may be greater than required by the type. The use of evaluation formats is characterized
1631 by the implementation-defined value of FLT_EVAL_METHOD:<sup><a href="#note19"><b>19)</b></a></sup>
1635 <!--page 37 -->
1636 <pre>
1637 -1 indeterminable;
1638 0 evaluate all operations and constants just to the range and precision of the
1639 type;
1640 1 evaluate operations and constants of type float and double to the
1641 range and precision of the double type, evaluate long double
1642 operations and constants to the range and precision of the long double
1643 type;
1644 2 evaluate all operations and constants to the range and precision of the
1645 long double type.</pre>
1646 All other negative values for FLT_EVAL_METHOD characterize implementation-defined
1647 behavior.
1649 The values given in the following list shall be replaced by constant expressions with
1650 implementation-defined values that are greater or equal in magnitude (absolute value) to
1651 those shown, with the same sign:
1652 <ul>
1653 <li> radix of exponent representation, b
1654 FLT_RADIX 2
1655 <li> number of base-FLT_RADIX digits in the floating-point significand, p
1656 FLT_MANT_DIG
1657 DBL_MANT_DIG
1658 LDBL_MANT_DIG
1659 <li> number of decimal digits, n, such that any floating-point number in the widest
1660 supported floating type with pmax radix b digits can be rounded to a floating-point
1661 number with n decimal digits and back again without change to the value,
1662 <pre>
1663 ??? pmax log10 b if b is a power of 10
1664 ???
1666 DECIMAL_DIG 10
1667 <li> number of decimal digits, q, such that any floating-point number with q decimal digits
1668 can be rounded into a floating-point number with p radix b digits and back again
1669 without change to the q decimal digits,
1674 <!--page 38 -->
1675 <pre>
1676 ??? p log10 b if b is a power of 10
1677 ???
1679 FLT_DIG 6
1680 DBL_DIG 10
1681 LDBL_DIG 10
1682 <li> minimum negative integer such that FLT_RADIX raised to one less than that power is
1683 a normalized floating-point number, emin
1684 FLT_MIN_EXP
1685 DBL_MIN_EXP
1686 LDBL_MIN_EXP
1688 normalized floating-point numbers, ???log10 b emin -1 ???
1689 <pre>
1690 ??? ???</pre>
1691 FLT_MIN_10_EXP -37
1692 DBL_MIN_10_EXP -37
1693 LDBL_MIN_10_EXP -37
1694 <li> maximum integer such that FLT_RADIX raised to one less than that power is a
1695 representable finite floating-point number, emax
1696 FLT_MAX_EXP
1697 DBL_MAX_EXP
1698 LDBL_MAX_EXP
1700 finite floating-point numbers, ???log10 ((1 - b- p )b emax )???
1701 FLT_MAX_10_EXP +37
1702 DBL_MAX_10_EXP +37
1703 LDBL_MAX_10_EXP +37
1704 </ul>
1706 The values given in the following list shall be replaced by constant expressions with
1707 implementation-defined values that are greater than or equal to those shown:
1708 <ul>
1710 FLT_MAX 1E+37
1711 DBL_MAX 1E+37
1712 LDBL_MAX 1E+37
1713 </ul>
1715 The values given in the following list shall be replaced by constant expressions with
1716 implementation-defined (positive) values that are less than or equal to those shown:
1717 <ul>
1719 given floating point type, b1- p
1720 <!--page 39 -->
1721 FLT_EPSILON 1E-5
1722 DBL_EPSILON 1E-9
1723 LDBL_EPSILON 1E-9
1725 FLT_MIN 1E-37
1726 DBL_MIN 1E-37
1727 LDBL_MIN 1E-37
1728 </ul>
1729 Recommended practice
1731 Conversion from (at least) double to decimal with DECIMAL_DIG digits and back
1732 should be the identity function.
1734 EXAMPLE 1 The following describes an artificial floating-point representation that meets the minimum
1735 requirements of this International Standard, and the appropriate values in a <a href="#7.7"><float.h></a> header for type
1736 float:
1737 <pre>
1738 6
1739 x = s16e (Sum) f k 16-k ,
1740 k=1
1743 <pre>
1744 FLT_RADIX 16
1745 FLT_MANT_DIG 6
1746 FLT_EPSILON 9.53674316E-07F
1747 FLT_DIG 6
1748 FLT_MIN_EXP -31
1749 FLT_MIN 2.93873588E-39F
1750 FLT_MIN_10_EXP -38
1751 FLT_MAX_EXP +32
1752 FLT_MAX 3.40282347E+38F
1756 EXAMPLE 2 The following describes floating-point representations that also meet the requirements for
1757 single-precision and double-precision normalized numbers in IEC 60559,<sup><a href="#note20"><b>20)</b></a></sup> and the appropriate values in a
1759 <pre>
1760 24
1761 x f = s2e (Sum) f k 2-k ,
1762 k=1
1765 <pre>
1766 53
1767 x d = s2e (Sum) f k 2-k ,
1768 k=1
1771 <pre>
1772 FLT_RADIX 2
1773 DECIMAL_DIG 17
1774 FLT_MANT_DIG 24
1775 FLT_EPSILON 1.19209290E-07F // decimal constant
1779 <!--page 40 -->
1780 <pre>
1781 FLT_DIG 6
1782 FLT_MIN_EXP -125
1783 FLT_MIN 1.17549435E-38F // decimal constant
1785 FLT_MIN_10_EXP -37
1786 FLT_MAX_EXP +128
1787 FLT_MAX 3.40282347E+38F // decimal constant
1788 FLT_MAX 0X1.fffffeP127F // hex constant
1789 FLT_MAX_10_EXP +38
1790 DBL_MANT_DIG 53
1791 DBL_EPSILON 2.2204460492503131E-16 // decimal constant
1793 DBL_DIG 15
1794 DBL_MIN_EXP -1021
1795 DBL_MIN 2.2250738585072014E-308 // decimal constant
1797 DBL_MIN_10_EXP -307
1798 DBL_MAX_EXP +1024
1799 DBL_MAX 1.7976931348623157E+308 // decimal constant
1800 DBL_MAX 0X1.fffffffffffffP1023 // hex constant
1802 If a type wider than double were supported, then DECIMAL_DIG would be greater than 17. For
1803 example, if the widest type were to use the minimal-width IEC 60559 double-extended format (64 bits of
1804 precision), then DECIMAL_DIG would be 21.
1806 <p><b> Forward references</b>: conditional inclusion (<a href="#6.10.1">6.10.1</a>), complex arithmetic
1807 <a href="#7.3"><complex.h></a> (<a href="#7.3">7.3</a>), extended multibyte and wide character utilities <a href="#7.24"><wchar.h></a>
1808 (<a href="#7.24">7.24</a>), floating-point environment <a href="#7.6"><fenv.h></a> (<a href="#7.6">7.6</a>), general utilities <a href="#7.20"><stdlib.h></a>
1809 (<a href="#7.20">7.20</a>), input/output <a href="#7.19"><stdio.h></a> (<a href="#7.19">7.19</a>), mathematics <a href="#7.12"><math.h></a> (<a href="#7.12">7.12</a>).
1810 <!--page 41 -->
1813 <p><small><a name="note16" href="#note16">16)</a> The floating-point model is intended to clarify the description of each floating-point characteristic and
1814 does not require the floating-point arithmetic of the implementation to be identical.
1815 </small>
1816 <p><small><a name="note17" href="#note17">17)</a> IEC 60559:1989 specifies quiet and signaling NaNs. For implementations that do not support
1818 similar behavior.
1819 </small>
1820 <p><small><a name="note18" href="#note18">18)</a> Evaluation of FLT_ROUNDS correctly reflects any execution-time change of rounding mode through
1822 </small>
1823 <p><small><a name="note19" href="#note19">19)</a> The evaluation method determines evaluation formats of expressions involving all floating types, not
1824 just real types. For example, if FLT_EVAL_METHOD is 1, then the product of two float
1825 _Complex operands is represented in the double _Complex format, and its parts are evaluated to
1826 double.
1827 </small>
1828 <p><small><a name="note20" href="#note20">20)</a> The floating-point model in that standard sums powers of b from zero, so the values of the exponent
1829 limits are one less than shown here.
1830 </small>
1836 In the syntax notation used in this clause, syntactic categories (nonterminals) are
1837 indicated by italic type, and literal words and character set members (terminals) by bold
1838 type. A colon (:) following a nonterminal introduces its definition. Alternative
1839 definitions are listed on separate lines, except when prefaced by the words ''one of''. An
1840 optional symbol is indicated by the subscript ''opt'', so that
1841 <pre>
1842 { expressionopt }</pre>
1843 indicates an optional expression enclosed in braces.
1845 When syntactic categories are referred to in the main text, they are not italicized and
1846 words are separated by spaces instead of hyphens.
1854 An identifier can denote an object; a function; a tag or a member of a structure, union, or
1855 enumeration; a typedef name; a label name; a macro name; or a macro parameter. The
1856 same identifier can denote different entities at different points in the program. A member
1857 of an enumeration is called an enumeration constant. Macro names and macro
1858 parameters are not considered further here, because prior to the semantic phase of
1859 program translation any occurrences of macro names in the source file are replaced by the
1860 preprocessing token sequences that constitute their macro definitions.
1862 For each different entity that an identifier designates, the identifier is visible (i.e., can be
1863 used) only within a region of program text called its scope. Different entities designated
1864 by the same identifier either have different scopes, or are in different name spaces. There
1865 are four kinds of scopes: function, file, block, and function prototype. (A function
1866 prototype is a declaration of a function that declares the types of its parameters.)
1868 A label name is the only kind of identifier that has function scope. It can be used (in a
1869 goto statement) anywhere in the function in which it appears, and is declared implicitly
1870 by its syntactic appearance (followed by a : and a statement).
1872 Every other identifier has scope determined by the placement of its declaration (in a
1873 declarator or type specifier). If the declarator or type specifier that declares the identifier
1874 appears outside of any block or list of parameters, the identifier has file scope, which
1875 terminates at the end of the translation unit. If the declarator or type specifier that
1876 declares the identifier appears inside a block or within the list of parameter declarations in
1877 a function definition, the identifier has block scope, which terminates at the end of the
1878 associated block. If the declarator or type specifier that declares the identifier appears
1879 <!--page 42 -->
1880 within the list of parameter declarations in a function prototype (not part of a function
1881 definition), the identifier has function prototype scope, which terminates at the end of the
1882 function declarator. If an identifier designates two different entities in the same name
1883 space, the scopes might overlap. If so, the scope of one entity (the inner scope) will be a
1884 strict subset of the scope of the other entity (the outer scope). Within the inner scope, the
1885 identifier designates the entity declared in the inner scope; the entity declared in the outer
1886 scope is hidden (and not visible) within the inner scope.
1888 Unless explicitly stated otherwise, where this International Standard uses the term
1889 ''identifier'' to refer to some entity (as opposed to the syntactic construct), it refers to the
1890 entity in the relevant name space whose declaration is visible at the point the identifier
1891 occurs.
1893 Two identifiers have the same scope if and only if their scopes terminate at the same
1894 point.
1896 Structure, union, and enumeration tags have scope that begins just after the appearance of
1897 the tag in a type specifier that declares the tag. Each enumeration constant has scope that
1898 begins just after the appearance of its defining enumerator in an enumerator list. Any
1899 other identifier has scope that begins just after the completion of its declarator.
1900 <p><b> Forward references</b>: declarations (<a href="#6.7">6.7</a>), function calls (<a href="#6.5.2.2">6.5.2.2</a>), function definitions
1901 (<a href="#6.9.1">6.9.1</a>), identifiers (<a href="#6.4.2">6.4.2</a>), name spaces of identifiers (<a href="#6.2.3">6.2.3</a>), macro replacement (<a href="#6.10.3">6.10.3</a>),
1906 An identifier declared in different scopes or in the same scope more than once can be
1907 made to refer to the same object or function by a process called linkage.<sup><a href="#note21"><b>21)</b></a></sup> There are
1908 three kinds of linkage: external, internal, and none.
1910 In the set of translation units and libraries that constitutes an entire program, each
1911 declaration of a particular identifier with external linkage denotes the same object or
1912 function. Within one translation unit, each declaration of an identifier with internal
1913 linkage denotes the same object or function. Each declaration of an identifier with no
1914 linkage denotes a unique entity.
1916 If the declaration of a file scope identifier for an object or a function contains the storage-
1917 class specifier static, the identifier has internal linkage.<sup><a href="#note22"><b>22)</b></a></sup>
1919 For an identifier declared with the storage-class specifier extern in a scope in which a
1923 <!--page 43 -->
1924 prior declaration of that identifier is visible,<sup><a href="#note23"><b>23)</b></a></sup> if the prior declaration specifies internal or
1925 external linkage, the linkage of the identifier at the later declaration is the same as the
1926 linkage specified at the prior declaration. If no prior declaration is visible, or if the prior
1927 declaration specifies no linkage, then the identifier has external linkage.
1929 If the declaration of an identifier for a function has no storage-class specifier, its linkage
1930 is determined exactly as if it were declared with the storage-class specifier extern. If
1931 the declaration of an identifier for an object has file scope and no storage-class specifier,
1932 its linkage is external.
1934 The following identifiers have no linkage: an identifier declared to be anything other than
1935 an object or a function; an identifier declared to be a function parameter; a block scope
1936 identifier for an object declared without the storage-class specifier extern.
1938 If, within a translation unit, the same identifier appears with both internal and external
1939 linkage, the behavior is undefined.
1940 <p><b> Forward references</b>: declarations (<a href="#6.7">6.7</a>), expressions (<a href="#6.5">6.5</a>), external definitions (<a href="#6.9">6.9</a>),
1944 <p><small><a name="note21" href="#note21">21)</a> There is no linkage between different identifiers.
1945 </small>
1946 <p><small><a name="note22" href="#note22">22)</a> A function declaration can contain the storage-class specifier static only if it is at file scope; see
1948 </small>
1949 <p><small><a name="note23" href="#note23">23)</a> As specified in <a href="#6.2.1">6.2.1</a>, the later declaration might hide the prior declaration.
1950 </small>
1954 If more than one declaration of a particular identifier is visible at any point in a
1955 translation unit, the syntactic context disambiguates uses that refer to different entities.
1956 Thus, there are separate name spaces for various categories of identifiers, as follows:
1957 <ul>
1958 <li> label names (disambiguated by the syntax of the label declaration and use);
1959 <li> the tags of structures, unions, and enumerations (disambiguated by following any<sup><a href="#note24"><b>24)</b></a></sup>
1960 of the keywords struct, union, or enum);
1961 <li> the members of structures or unions; each structure or union has a separate name
1962 space for its members (disambiguated by the type of the expression used to access the
1963 member via the . or -> operator);
1964 <li> all other identifiers, called ordinary identifiers (declared in ordinary declarators or as
1965 enumeration constants).
1966 </ul>
1967 <p><b> Forward references</b>: enumeration specifiers (<a href="#6.7.2.2">6.7.2.2</a>), labeled statements (<a href="#6.8.1">6.8.1</a>),
1968 structure and union specifiers (<a href="#6.7.2.1">6.7.2.1</a>), structure and union members (<a href="#6.5.2.3">6.5.2.3</a>), tags
1974 <!--page 44 -->
1977 <p><small><a name="note24" href="#note24">24)</a> There is only one name space for tags even though three are possible.
1978 </small>
1982 An object has a storage duration that determines its lifetime. There are three storage
1983 durations: static, automatic, and allocated. Allocated storage is described in <a href="#7.20.3">7.20.3</a>.
1985 The lifetime of an object is the portion of program execution during which storage is
1986 guaranteed to be reserved for it. An object exists, has a constant address,<sup><a href="#note25"><b>25)</b></a></sup> and retains
1987 its last-stored value throughout its lifetime.<sup><a href="#note26"><b>26)</b></a></sup> If an object is referred to outside of its
1988 lifetime, the behavior is undefined. The value of a pointer becomes indeterminate when
1989 the object it points to reaches the end of its lifetime.
1991 An object whose identifier is declared with external or internal linkage, or with the
1992 storage-class specifier static has static storage duration. Its lifetime is the entire
1993 execution of the program and its stored value is initialized only once, prior to program
1994 startup.
1996 An object whose identifier is declared with no linkage and without the storage-class
1997 specifier static has automatic storage duration.
1999 For such an object that does not have a variable length array type, its lifetime extends
2000 from entry into the block with which it is associated until execution of that block ends in
2001 any way. (Entering an enclosed block or calling a function suspends, but does not end,
2002 execution of the current block.) If the block is entered recursively, a new instance of the
2003 object is created each time. The initial value of the object is indeterminate. If an
2004 initialization is specified for the object, it is performed each time the declaration is
2005 reached in the execution of the block; otherwise, the value becomes indeterminate each
2006 time the declaration is reached.
2008 For such an object that does have a variable length array type, its lifetime extends from
2009 the declaration of the object until execution of the program leaves the scope of the
2010 declaration.<sup><a href="#note27"><b>27)</b></a></sup> If the scope is entered recursively, a new instance of the object is created
2011 each time. The initial value of the object is indeterminate.
2012 <p><b> Forward references</b>: statements (<a href="#6.8">6.8</a>), function calls (<a href="#6.5.2.2">6.5.2.2</a>), declarators (<a href="#6.7.5">6.7.5</a>), array
2018 <!--page 45 -->
2021 <p><small><a name="note25" href="#note25">25)</a> The term ''constant address'' means that two pointers to the object constructed at possibly different
2022 times will compare equal. The address may be different during two different executions of the same
2023 program.
2024 </small>
2025 <p><small><a name="note26" href="#note26">26)</a> In the case of a volatile object, the last store need not be explicit in the program.
2026 </small>
2027 <p><small><a name="note27" href="#note27">27)</a> Leaving the innermost block containing the declaration, or jumping to a point in that block or an
2028 embedded block prior to the declaration, leaves the scope of the declaration.
2029 </small>
2033 The meaning of a value stored in an object or returned by a function is determined by the
2034 type of the expression used to access it. (An identifier declared to be an object is the
2035 simplest such expression; the type is specified in the declaration of the identifier.) Types
2036 are partitioned into object types (types that fully describe objects), function types (types
2037 that describe functions), and incomplete types (types that describe objects but lack
2038 information needed to determine their sizes).
2042 An object declared as type char is large enough to store any member of the basic
2043 execution character set. If a member of the basic execution character set is stored in a
2044 char object, its value is guaranteed to be nonnegative. If any other character is stored in
2045 a char object, the resulting value is implementation-defined but shall be within the range
2046 of values that can be represented in that type.
2048 There are five standard signed integer types, designated as signed char, short
2049 int, int, long int, and long long int. (These and other types may be
2050 designated in several additional ways, as described in <a href="#6.7.2">6.7.2</a>.) There may also be
2051 implementation-defined extended signed integer types.<sup><a href="#note28"><b>28)</b></a></sup> The standard and extended
2052 signed integer types are collectively called signed integer types.<sup><a href="#note29"><b>29)</b></a></sup>
2054 An object declared as type signed char occupies the same amount of storage as a
2055 ''plain'' char object. A ''plain'' int object has the natural size suggested by the
2056 architecture of the execution environment (large enough to contain any value in the range
2059 For each of the signed integer types, there is a corresponding (but different) unsigned
2060 integer type (designated with the keyword unsigned) that uses the same amount of
2061 storage (including sign information) and has the same alignment requirements. The type
2062 _Bool and the unsigned integer types that correspond to the standard signed integer
2063 types are the standard unsigned integer types. The unsigned integer types that
2064 correspond to the extended signed integer types are the extended unsigned integer types.
2065 The standard and extended unsigned integer types are collectively called unsigned integer
2070 <!--page 46 -->
2072 The standard signed integer types and standard unsigned integer types are collectively
2073 called the standard integer types, the extended signed integer types and extended
2074 unsigned integer types are collectively called the extended integer types.
2076 For any two integer types with the same signedness and different integer conversion rank
2077 (see <a href="#6.3.1.1">6.3.1.1</a>), the range of values of the type with smaller integer conversion rank is a
2078 subrange of the values of the other type.
2080 The range of nonnegative values of a signed integer type is a subrange of the
2081 corresponding unsigned integer type, and the representation of the same value in each
2082 type is the same.<sup><a href="#note31"><b>31)</b></a></sup> A computation involving unsigned operands can never overflow,
2083 because a result that cannot be represented by the resulting unsigned integer type is
2084 reduced modulo the number that is one greater than the largest value that can be
2085 represented by the resulting type.
2087 There are three real floating types, designated as float, double, and long
2088 double.<sup><a href="#note32"><b>32)</b></a></sup> The set of values of the type float is a subset of the set of values of the
2089 type double; the set of values of the type double is a subset of the set of values of the
2090 type long double.
2092 There are three complex types, designated as float _Complex, double
2093 _Complex, and long double _Complex.<sup><a href="#note33"><b>33)</b></a></sup> The real floating and complex types
2094 are collectively called the floating types.
2096 For each floating type there is a corresponding real type, which is always a real floating
2097 type. For real floating types, it is the same type. For complex types, it is the type given
2098 by deleting the keyword _Complex from the type name.
2100 Each complex type has the same representation and alignment requirements as an array
2101 type containing exactly two elements of the corresponding real type; the first element is
2102 equal to the real part, and the second element to the imaginary part, of the complex
2103 number.
2105 The type char, the signed and unsigned integer types, and the floating types are
2106 collectively called the basic types. Even if the implementation defines two or more basic
2107 types to have the same representation, they are nevertheless different types.<sup><a href="#note34"><b>34)</b></a></sup>
2109 <!--page 47 -->
2111 The three types char, signed char, and unsigned char are collectively called
2112 the character types. The implementation shall define char to have the same range,
2113 representation, and behavior as either signed char or unsigned char.<sup><a href="#note35"><b>35)</b></a></sup>
2115 An enumeration comprises a set of named integer constant values. Each distinct
2116 enumeration constitutes a different enumerated type.
2118 The type char, the signed and unsigned integer types, and the enumerated types are
2119 collectively called integer types. The integer and real floating types are collectively called
2120 real types.
2122 Integer and floating types are collectively called arithmetic types. Each arithmetic type
2123 belongs to one type domain: the real type domain comprises the real types, the complex
2124 type domain comprises the complex types.
2126 The void type comprises an empty set of values; it is an incomplete type that cannot be
2127 completed.
2129 Any number of derived types can be constructed from the object, function, and
2130 incomplete types, as follows:
2131 <ul>
2132 <li> An array type describes a contiguously allocated nonempty set of objects with a
2133 particular member object type, called the element type.<sup><a href="#note36"><b>36)</b></a></sup> Array types are
2134 characterized by their element type and by the number of elements in the array. An
2135 array type is said to be derived from its element type, and if its element type is T , the
2136 array type is sometimes called ''array of T ''. The construction of an array type from
2137 an element type is called ''array type derivation''.
2138 <li> A structure type describes a sequentially allocated nonempty set of member objects
2139 (and, in certain circumstances, an incomplete array), each of which has an optionally
2140 specified name and possibly distinct type.
2141 <li> A union type describes an overlapping nonempty set of member objects, each of
2142 which has an optionally specified name and possibly distinct type.
2143 <li> A function type describes a function with specified return type. A function type is
2144 characterized by its return type and the number and types of its parameters. A
2145 function type is said to be derived from its return type, and if its return type is T , the
2146 function type is sometimes called ''function returning T ''. The construction of a
2147 function type from a return type is called ''function type derivation''.
2151 <!--page 48 -->
2152 <li> A pointer type may be derived from a function type, an object type, or an incomplete
2153 type, called the referenced type. A pointer type describes an object whose value
2154 provides a reference to an entity of the referenced type. A pointer type derived from
2155 the referenced type T is sometimes called ''pointer to T ''. The construction of a
2156 pointer type from a referenced type is called ''pointer type derivation''.
2157 </ul>
2158 These methods of constructing derived types can be applied recursively.
2160 Arithmetic types and pointer types are collectively called scalar types. Array and
2161 structure types are collectively called aggregate types.<sup><a href="#note37"><b>37)</b></a></sup>
2163 An array type of unknown size is an incomplete type. It is completed, for an identifier of
2164 that type, by specifying the size in a later declaration (with internal or external linkage).
2165 A structure or union type of unknown content (as described in <a href="#6.7.2.3">6.7.2.3</a>) is an incomplete
2166 type. It is completed, for all declarations of that type, by declaring the same structure or
2167 union tag with its defining content later in the same scope.
2169 A type has known constant size if the type is not incomplete and is not a variable length
2170 array type.
2172 Array, function, and pointer types are collectively called derived declarator types. A
2173 declarator type derivation from a type T is the construction of a derived declarator type
2174 from T by the application of an array-type, a function-type, or a pointer-type derivation to
2175 T.
2177 A type is characterized by its type category, which is either the outermost derivation of a
2178 derived type (as noted above in the construction of derived types), or the type itself if the
2179 type consists of no derived types.
2181 Any type so far mentioned is an unqualified type. Each unqualified type has several
2182 qualified versions of its type,<sup><a href="#note38"><b>38)</b></a></sup> corresponding to the combinations of one, two, or all
2183 three of the const, volatile, and restrict qualifiers. The qualified or unqualified
2184 versions of a type are distinct types that belong to the same type category and have the
2185 same representation and alignment requirements.<sup><a href="#note39"><b>39)</b></a></sup> A derived type is not qualified by the
2186 qualifiers (if any) of the type from which it is derived.
2188 A pointer to void shall have the same representation and alignment requirements as a
2189 pointer to a character type.39) Similarly, pointers to qualified or unqualified versions of
2190 compatible types shall have the same representation and alignment requirements. All
2193 <!--page 49 -->
2194 pointers to structure types shall have the same representation and alignment requirements
2195 as each other. All pointers to union types shall have the same representation and
2196 alignment requirements as each other. Pointers to other types need not have the same
2197 representation or alignment requirements.
2199 EXAMPLE 1 The type designated as ''float *'' has type ''pointer to float''. Its type category is
2200 pointer, not a floating type. The const-qualified version of this type is designated as ''float * const''
2201 whereas the type designated as ''const float *'' is not a qualified type -- its type is ''pointer to const-
2202 qualified float'' and is a pointer to a qualified type.
2206 function returning struct tag''. The array has length five and the function has a single parameter of type
2207 float. Its type category is array.
2209 <p><b> Forward references</b>: compatible type and composite type (<a href="#6.2.7">6.2.7</a>), declarations (<a href="#6.7">6.7</a>).
2212 <p><small><a name="note28" href="#note28">28)</a> Implementation-defined keywords shall have the form of an identifier reserved for any use as
2214 </small>
2215 <p><small><a name="note29" href="#note29">29)</a> Therefore, any statement in this Standard about signed integer types also applies to the extended
2216 signed integer types.
2217 </small>
2218 <p><small><a name="note30" href="#note30">30)</a> Therefore, any statement in this Standard about unsigned integer types also applies to the extended
2219 unsigned integer types.
2220 </small>
2221 <p><small><a name="note31" href="#note31">31)</a> The same representation and alignment requirements are meant to imply interchangeability as
2222 arguments to functions, return values from functions, and members of unions.
2223 </small>
2224 <p><small><a name="note32" href="#note32">32)</a> See ''future language directions'' (<a href="#6.11.1">6.11.1</a>).
2225 </small>
2226 <p><small><a name="note33" href="#note33">33)</a> A specification for imaginary types is in informative <a href="#G">annex G</a>.
2227 </small>
2228 <p><small><a name="note34" href="#note34">34)</a> An implementation may define new keywords that provide alternative ways to designate a basic (or
2229 any other) type; this does not violate the requirement that all basic types be different.
2230 Implementation-defined keywords shall have the form of an identifier reserved for any use as
2232 </small>
2233 <p><small><a name="note35" href="#note35">35)</a> CHAR_MIN, defined in <a href="#7.10"><limits.h></a>, will have one of the values 0 or SCHAR_MIN, and this can be
2234 used to distinguish the two options. Irrespective of the choice made, char is a separate type from the
2235 other two and is not compatible with either.
2236 </small>
2237 <p><small><a name="note36" href="#note36">36)</a> Since object types do not include incomplete types, an array of incomplete type cannot be constructed.
2238 </small>
2239 <p><small><a name="note37" href="#note37">37)</a> Note that aggregate type does not include union type because an object with union type can only
2240 contain one member at a time.
2241 </small>
2242 <p><small><a name="note38" href="#note38">38)</a> See <a href="#6.7.3">6.7.3</a> regarding qualified array and function types.
2243 </small>
2244 <p><small><a name="note39" href="#note39">39)</a> The same representation and alignment requirements are meant to imply interchangeability as
2245 arguments to functions, return values from functions, and members of unions.
2246 </small>
2252 The representations of all types are unspecified except as stated in this subclause.
2254 Except for bit-fields, objects are composed of contiguous sequences of one or more bytes,
2255 the number, order, and encoding of which are either explicitly specified or
2256 implementation-defined.
2258 Values stored in unsigned bit-fields and objects of type unsigned char shall be
2261 Values stored in non-bit-field objects of any other object type consist of n x CHAR_BIT
2262 bits, where n is the size of an object of that type, in bytes. The value may be copied into
2263 an object of type unsigned char [n] (e.g., by memcpy); the resulting set of bytes is
2264 called the object representation of the value. Values stored in bit-fields consist of m bits,
2265 where m is the size specified for the bit-field. The object representation is the set of m
2266 bits the bit-field comprises in the addressable storage unit holding it. Two values (other
2267 than NaNs) with the same object representation compare equal, but values that compare
2268 equal may have different object representations.
2270 Certain object representations need not represent a value of the object type. If the stored
2271 value of an object has such a representation and is read by an lvalue expression that does
2272 not have character type, the behavior is undefined. If such a representation is produced
2273 by a side effect that modifies all or any part of the object by an lvalue expression that
2274 does not have character type, the behavior is undefined.<sup><a href="#note41"><b>41)</b></a></sup> Such a representation is called
2276 <!--page 50 -->
2277 a trap representation.
2279 When a value is stored in an object of structure or union type, including in a member
2280 object, the bytes of the object representation that correspond to any padding bytes take
2281 unspecified values.<sup><a href="#note42"><b>42)</b></a></sup> The value of a structure or union object is never a trap
2282 representation, even though the value of a member of the structure or union object may be
2283 a trap representation.
2285 When a value is stored in a member of an object of union type, the bytes of the object
2286 representation that do not correspond to that member but do correspond to other members
2287 take unspecified values.
2289 Where an operator is applied to a value that has more than one object representation,
2290 which object representation is used shall not affect the value of the result.<sup><a href="#note43"><b>43)</b></a></sup> Where a
2291 value is stored in an object using a type that has more than one object representation for
2292 that value, it is unspecified which representation is used, but a trap representation shall
2293 not be generated.
2294 <p><b> Forward references</b>: declarations (<a href="#6.7">6.7</a>), expressions (<a href="#6.5">6.5</a>), lvalues, arrays, and function
2298 <p><small><a name="note40" href="#note40">40)</a> A positional representation for integers that uses the binary digits 0 and 1, in which the values
2299 represented by successive bits are additive, begin with 1, and are multiplied by successive integral
2300 powers of 2, except perhaps the bit with the highest position. (Adapted from the American National
2301 Dictionary for Information Processing Systems.) A byte contains CHAR_BIT bits, and the values of
2304 <pre>
2305 CHAR_BIT
2307 </small>
2308 <p><small><a name="note41" href="#note41">41)</a> Thus, an automatic variable can be initialized to a trap representation without causing undefined
2309 behavior, but the value of the variable cannot be used until a proper value is stored in it.
2310 </small>
2311 <p><small><a name="note42" href="#note42">42)</a> Thus, for example, structure assignment need not copy any padding bits.
2312 </small>
2313 <p><small><a name="note43" href="#note43">43)</a> It is possible for objects x and y with the same effective type T to have the same value when they are
2314 accessed as objects of type T, but to have different values in other contexts. In particular, if == is
2316 Furthermore, x == y does not necessarily imply that x and y have the same value; other operations
2317 on values of type T may distinguish between them.
2318 </small>
2322 For unsigned integer types other than unsigned char, the bits of the object
2323 representation shall be divided into two groups: value bits and padding bits (there need
2324 not be any of the latter). If there are N value bits, each bit shall represent a different
2327 known as the value representation. The values of any padding bits are unspecified.<sup><a href="#note44"><b>44)</b></a></sup>
2329 For signed integer types, the bits of the object representation shall be divided into three
2330 groups: value bits, padding bits, and the sign bit. There need not be any padding bits;
2332 <!--page 51 -->
2333 there shall be exactly one sign bit. Each bit that is a value bit shall have the same value as
2334 the same bit in the object representation of the corresponding unsigned type (if there are
2335 M value bits in the signed type and N in the unsigned type, then M <= N ). If the sign bit
2336 is zero, it shall not affect the resulting value. If the sign bit is one, the value shall be
2337 modified in one of the following ways:
2338 <ul>
2342 </ul>
2343 Which of these applies is implementation-defined, as is whether the value with sign bit 1
2344 and all value bits zero (for the first two), or with sign bit and all value bits 1 (for ones'
2345 complement), is a trap representation or a normal value. In the case of sign and
2346 magnitude and ones' complement, if this representation is a normal value it is called a
2347 negative zero.
2349 If the implementation supports negative zeros, they shall be generated only by:
2350 <ul>
2351 <li> the &, |, ^, ~, <<, and >> operators with arguments that produce such a value;
2352 <li> the +, -, *, /, and % operators where one argument is a negative zero and the result is
2353 zero;
2354 <li> compound assignment operators based on the above cases.
2355 </ul>
2356 It is unspecified whether these cases actually generate a negative zero or a normal zero,
2357 and whether a negative zero becomes a normal zero when stored in an object.
2359 If the implementation does not support negative zeros, the behavior of the &, |, ^, ~, <<,
2360 and >> operators with arguments that would produce such a value is undefined.
2362 The values of any padding bits are unspecified.<sup><a href="#note45"><b>45)</b></a></sup> A valid (non-trap) object representation
2363 of a signed integer type where the sign bit is zero is a valid object representation of the
2364 corresponding unsigned type, and shall represent the same value. For any integer type,
2365 the object representation where all the bits are zero shall be a representation of the value
2366 zero in that type.
2368 The precision of an integer type is the number of bits it uses to represent values,
2369 excluding any sign and padding bits. The width of an integer type is the same but
2370 including any sign bit; thus for unsigned integer types the two values are the same, while
2373 <!--page 52 -->
2374 for signed integer types the width is one greater than the precision.
2377 <p><small><a name="note44" href="#note44">44)</a> Some combinations of padding bits might generate trap representations, for example, if one padding
2378 bit is a parity bit. Regardless, no arithmetic operation on valid values can generate a trap
2379 representation other than as part of an exceptional condition such as an overflow, and this cannot occur
2380 with unsigned types. All other combinations of padding bits are alternative object representations of
2381 the value specified by the value bits.
2382 </small>
2383 <p><small><a name="note45" href="#note45">45)</a> Some combinations of padding bits might generate trap representations, for example, if one padding
2384 bit is a parity bit. Regardless, no arithmetic operation on valid values can generate a trap
2385 representation other than as part of an exceptional condition such as an overflow. All other
2386 combinations of padding bits are alternative object representations of the value specified by the value
2387 bits.
2388 </small>
2392 Two types have compatible type if their types are the same. Additional rules for
2393 determining whether two types are compatible are described in <a href="#6.7.2">6.7.2</a> for type specifiers,
2394 in <a href="#6.7.3">6.7.3</a> for type qualifiers, and in <a href="#6.7.5">6.7.5</a> for declarators.<sup><a href="#note46"><b>46)</b></a></sup> Moreover, two structure,
2395 union, or enumerated types declared in separate translation units are compatible if their
2396 tags and members satisfy the following requirements: If one is declared with a tag, the
2397 other shall be declared with the same tag. If both are complete types, then the following
2398 additional requirements apply: there shall be a one-to-one correspondence between their
2399 members such that each pair of corresponding members are declared with compatible
2400 types, and such that if one member of a corresponding pair is declared with a name, the
2401 other member is declared with the same name. For two structures, corresponding
2402 members shall be declared in the same order. For two structures or unions, corresponding
2403 bit-fields shall have the same widths. For two enumerations, corresponding members
2404 shall have the same values.
2406 All declarations that refer to the same object or function shall have compatible type;
2407 otherwise, the behavior is undefined.
2409 A composite type can be constructed from two types that are compatible; it is a type that
2410 is compatible with both of the two types and satisfies the following conditions:
2411 <ul>
2412 <li> If one type is an array of known constant size, the composite type is an array of that
2413 size; otherwise, if one type is a variable length array, the composite type is that type.
2414 <li> If only one type is a function type with a parameter type list (a function prototype),
2415 the composite type is a function prototype with the parameter type list.
2416 <li> If both types are function types with parameter type lists, the type of each parameter
2417 in the composite parameter type list is the composite type of the corresponding
2418 parameters.
2419 </ul>
2420 These rules apply recursively to the types from which the two types are derived.
2422 For an identifier with internal or external linkage declared in a scope in which a prior
2423 declaration of that identifier is visible,<sup><a href="#note47"><b>47)</b></a></sup> if the prior declaration specifies internal or
2424 external linkage, the type of the identifier at the later declaration becomes the composite
2425 type.
2430 <!--page 53 -->
2432 EXAMPLE Given the following two file scope declarations:
2433 <pre>
2434 int f(int (*)(), double (*)[3]);
2435 int f(int (*)(char *), double (*)[]);</pre>
2436 The resulting composite type for the function is:
2437 <!--page 54 -->
2438 <pre>
2442 <p><small><a name="note46" href="#note46">46)</a> Two types need not be identical to be compatible.
2443 </small>
2444 <p><small><a name="note47" href="#note47">47)</a> As specified in <a href="#6.2.1">6.2.1</a>, the later declaration might hide the prior declaration.
2445 </small>
2449 Several operators convert operand values from one type to another automatically. This
2450 subclause specifies the result required from such an implicit conversion, as well as those
2451 that result from a cast operation (an explicit conversion). The list in <a href="#6.3.1.8">6.3.1.8</a> summarizes
2452 the conversions performed by most ordinary operators; it is supplemented as required by
2455 Conversion of an operand value to a compatible type causes no change to the value or the
2456 representation.
2463 Every integer type has an integer conversion rank defined as follows:
2464 <ul>
2465 <li> No two signed integer types shall have the same rank, even if they have the same
2466 representation.
2467 <li> The rank of a signed integer type shall be greater than the rank of any signed integer
2468 type with less precision.
2469 <li> The rank of long long int shall be greater than the rank of long int, which
2470 shall be greater than the rank of int, which shall be greater than the rank of short
2471 int, which shall be greater than the rank of signed char.
2472 <li> The rank of any unsigned integer type shall equal the rank of the corresponding
2473 signed integer type, if any.
2474 <li> The rank of any standard integer type shall be greater than the rank of any extended
2475 integer type with the same width.
2476 <li> The rank of char shall equal the rank of signed char and unsigned char.
2477 <li> The rank of _Bool shall be less than the rank of all other standard integer types.
2478 <li> The rank of any enumerated type shall equal the rank of the compatible integer type
2480 <li> The rank of any extended signed integer type relative to another extended signed
2481 integer type with the same precision is implementation-defined, but still subject to the
2482 other rules for determining the integer conversion rank.
2483 <li> For all integer types T1, T2, and T3, if T1 has greater rank than T2 and T2 has
2484 greater rank than T3, then T1 has greater rank than T3.
2485 </ul>
2487 The following may be used in an expression wherever an int or unsigned int may
2488 be used:
2489 <!--page 55 -->
2490 <ul>
2491 <li> An object or expression with an integer type whose integer conversion rank is less
2492 than or equal to the rank of int and unsigned int.
2493 <li> A bit-field of type _Bool, int, signed int, or unsigned int.
2494 </ul>
2495 If an int can represent all values of the original type, the value is converted to an int;
2496 otherwise, it is converted to an unsigned int. These are called the integer
2497 promotions.<sup><a href="#note48"><b>48)</b></a></sup> All other types are unchanged by the integer promotions.
2499 The integer promotions preserve value including sign. As discussed earlier, whether a
2500 ''plain'' char is treated as signed is implementation-defined.
2501 <p><b> Forward references</b>: enumeration specifiers (<a href="#6.7.2.2">6.7.2.2</a>), structure and union specifiers
2505 <p><small><a name="note48" href="#note48">48)</a> The integer promotions are applied only: as part of the usual arithmetic conversions, to certain
2506 argument expressions, to the operands of the unary +, -, and ~ operators, and to both operands of the
2507 shift operators, as specified by their respective subclauses.
2508 </small>
2512 When any scalar value is converted to _Bool, the result is 0 if the value compares equal
2517 When a value with integer type is converted to another integer type other than _Bool, if
2518 the value can be represented by the new type, it is unchanged.
2520 Otherwise, if the new type is unsigned, the value is converted by repeatedly adding or
2521 subtracting one more than the maximum value that can be represented in the new type
2524 Otherwise, the new type is signed and the value cannot be represented in it; either the
2525 result is implementation-defined or an implementation-defined signal is raised.
2528 <p><small><a name="note49" href="#note49">49)</a> The rules describe arithmetic on the mathematical value, not the value of a given type of expression.
2529 </small>
2533 When a finite value of real floating type is converted to an integer type other than _Bool,
2534 the fractional part is discarded (i.e., the value is truncated toward zero). If the value of
2535 the integral part cannot be represented by the integer type, the behavior is undefined.<sup><a href="#note50"><b>50)</b></a></sup>
2537 When a value of integer type is converted to a real floating type, if the value being
2538 converted can be represented exactly in the new type, it is unchanged. If the value being
2539 converted is in the range of values that can be represented but cannot be represented
2541 <!--page 56 -->
2542 exactly, the result is either the nearest higher or nearest lower representable value, chosen
2543 in an implementation-defined manner. If the value being converted is outside the range of
2544 values that can be represented, the behavior is undefined.
2547 <p><small><a name="note50" href="#note50">50)</a> The remaindering operation performed when a value of integer type is converted to unsigned type
2548 need not be performed when a value of real floating type is converted to unsigned type. Thus, the
2550 </small>
2554 When a float is promoted to double or long double, or a double is promoted
2555 to long double, its value is unchanged (if the source value is represented in the
2556 precision and range of its type).
2558 When a double is demoted to float, a long double is demoted to double or
2559 float, or a value being represented in greater precision and range than required by its
2560 semantic type (see <a href="#6.3.1.8">6.3.1.8</a>) is explicitly converted (including to its own type), if the value
2561 being converted can be represented exactly in the new type, it is unchanged. If the value
2562 being converted is in the range of values that can be represented but cannot be
2563 represented exactly, the result is either the nearest higher or nearest lower representable
2564 value, chosen in an implementation-defined manner. If the value being converted is
2565 outside the range of values that can be represented, the behavior is undefined.
2569 When a value of complex type is converted to another complex type, both the real and
2570 imaginary parts follow the conversion rules for the corresponding real types.
2574 When a value of real type is converted to a complex type, the real part of the complex
2575 result value is determined by the rules of conversion to the corresponding real type and
2576 the imaginary part of the complex result value is a positive zero or an unsigned zero.
2578 When a value of complex type is converted to a real type, the imaginary part of the
2579 complex value is discarded and the value of the real part is converted according to the
2580 conversion rules for the corresponding real type.
2584 Many operators that expect operands of arithmetic type cause conversions and yield result
2585 types in a similar way. The purpose is to determine a common real type for the operands
2586 and result. For the specified operands, each operand is converted, without change of type
2587 domain, to a type whose corresponding real type is the common real type. Unless
2588 explicitly stated otherwise, the common real type is also the corresponding real type of
2589 the result, whose type domain is the type domain of the operands if they are the same,
2590 and complex otherwise. This pattern is called the usual arithmetic conversions:
2591 <!--page 57 -->
2593 <pre>
2594 First, if the corresponding real type of either operand is long double, the other
2595 operand is converted, without change of type domain, to a type whose
2596 corresponding real type is long double.
2597 Otherwise, if the corresponding real type of either operand is double, the other
2598 operand is converted, without change of type domain, to a type whose
2599 corresponding real type is double.
2600 Otherwise, if the corresponding real type of either operand is float, the other
2601 operand is converted, without change of type domain, to a type whose
2603 Otherwise, the integer promotions are performed on both operands. Then the
2604 following rules are applied to the promoted operands:
2605 If both operands have the same type, then no further conversion is needed.
2606 Otherwise, if both operands have signed integer types or both have unsigned
2607 integer types, the operand with the type of lesser integer conversion rank is
2608 converted to the type of the operand with greater rank.
2609 Otherwise, if the operand that has unsigned integer type has rank greater or
2610 equal to the rank of the type of the other operand, then the operand with
2611 signed integer type is converted to the type of the operand with unsigned
2612 integer type.
2613 Otherwise, if the type of the operand with signed integer type can represent
2614 all of the values of the type of the operand with unsigned integer type, then
2615 the operand with unsigned integer type is converted to the type of the
2616 operand with signed integer type.
2617 Otherwise, both operands are converted to the unsigned integer type
2618 corresponding to the type of the operand with signed integer type.</pre>
2619 The values of floating operands and of the results of floating expressions may be
2620 represented in greater precision and range than that required by the type; the types are not
2626 <!--page 58 -->
2629 <p><small><a name="note51" href="#note51">51)</a> For example, addition of a double _Complex and a float entails just the conversion of the
2630 float operand to double (and yields a double _Complex result).
2631 </small>
2632 <p><small><a name="note52" href="#note52">52)</a> The cast and assignment operators are still required to perform their specified conversions as
2634 </small>
2638 <h5><a name="6.3.2.1" href="#6.3.2.1">6.3.2.1 Lvalues, arrays, and function designators</a></h5>
2640 An lvalue is an expression with an object type or an incomplete type other than void;<sup><a href="#note53"><b>53)</b></a></sup>
2641 if an lvalue does not designate an object when it is evaluated, the behavior is undefined.
2642 When an object is said to have a particular type, the type is specified by the lvalue used to
2643 designate the object. A modifiable lvalue is an lvalue that does not have array type, does
2644 not have an incomplete type, does not have a const-qualified type, and if it is a structure
2645 or union, does not have any member (including, recursively, any member or element of
2646 all contained aggregates or unions) with a const-qualified type.
2648 Except when it is the operand of the sizeof operator, the unary & operator, the ++
2649 operator, the -- operator, or the left operand of the . operator or an assignment operator,
2650 an lvalue that does not have array type is converted to the value stored in the designated
2651 object (and is no longer an lvalue). If the lvalue has qualified type, the value has the
2652 unqualified version of the type of the lvalue; otherwise, the value has the type of the
2653 lvalue. If the lvalue has an incomplete type and does not have array type, the behavior is
2654 undefined.
2656 Except when it is the operand of the sizeof operator or the unary & operator, or is a
2657 string literal used to initialize an array, an expression that has type ''array of type'' is
2658 converted to an expression with type ''pointer to type'' that points to the initial element of
2659 the array object and is not an lvalue. If the array object has register storage class, the
2660 behavior is undefined.
2662 A function designator is an expression that has function type. Except when it is the
2663 operand of the sizeof operator<sup><a href="#note54"><b>54)</b></a></sup> or the unary & operator, a function designator with
2664 type ''function returning type'' is converted to an expression that has type ''pointer to
2665 function returning type''.
2666 <p><b> Forward references</b>: address and indirection operators (<a href="#6.5.3.2">6.5.3.2</a>), assignment operators
2667 (<a href="#6.5.16">6.5.16</a>), common definitions <a href="#7.17"><stddef.h></a> (<a href="#7.17">7.17</a>), initialization (<a href="#6.7.8">6.7.8</a>), postfix
2668 increment and decrement operators (<a href="#6.5.2.4">6.5.2.4</a>), prefix increment and decrement operators
2669 (<a href="#6.5.3.1">6.5.3.1</a>), the sizeof operator (<a href="#6.5.3.4">6.5.3.4</a>), structure and union members (<a href="#6.5.2.3">6.5.2.3</a>).
2672 <!--page 59 -->
2675 <p><small><a name="note53" href="#note53">53)</a> The name ''lvalue'' comes originally from the assignment expression E1 = E2, in which the left
2676 operand E1 is required to be a (modifiable) lvalue. It is perhaps better considered as representing an
2677 object ''locator value''. What is sometimes called ''rvalue'' is in this International Standard described
2678 as the ''value of an expression''.
2679 An obvious example of an lvalue is an identifier of an object. As a further example, if E is a unary
2680 expression that is a pointer to an object, *E is an lvalue that designates the object to which E points.
2681 </small>
2682 <p><small><a name="note54" href="#note54">54)</a> Because this conversion does not occur, the operand of the sizeof operator remains a function
2684 </small>
2688 The (nonexistent) value of a void expression (an expression that has type void) shall not
2689 be used in any way, and implicit or explicit conversions (except to void) shall not be
2690 applied to such an expression. If an expression of any other type is evaluated as a void
2691 expression, its value or designator is discarded. (A void expression is evaluated for its
2692 side effects.)
2696 A pointer to void may be converted to or from a pointer to any incomplete or object
2697 type. A pointer to any incomplete or object type may be converted to a pointer to void
2698 and back again; the result shall compare equal to the original pointer.
2700 For any qualifier q, a pointer to a non-q-qualified type may be converted to a pointer to
2701 the q-qualified version of the type; the values stored in the original and converted pointers
2702 shall compare equal.
2704 An integer constant expression with the value 0, or such an expression cast to type
2705 void *, is called a null pointer constant.<sup><a href="#note55"><b>55)</b></a></sup> If a null pointer constant is converted to a
2706 pointer type, the resulting pointer, called a null pointer, is guaranteed to compare unequal
2707 to a pointer to any object or function.
2709 Conversion of a null pointer to another pointer type yields a null pointer of that type.
2710 Any two null pointers shall compare equal.
2712 An integer may be converted to any pointer type. Except as previously specified, the
2713 result is implementation-defined, might not be correctly aligned, might not point to an
2714 entity of the referenced type, and might be a trap representation.<sup><a href="#note56"><b>56)</b></a></sup>
2716 Any pointer type may be converted to an integer type. Except as previously specified, the
2717 result is implementation-defined. If the result cannot be represented in the integer type,
2718 the behavior is undefined. The result need not be in the range of values of any integer
2719 type.
2721 A pointer to an object or incomplete type may be converted to a pointer to a different
2722 object or incomplete type. If the resulting pointer is not correctly aligned<sup><a href="#note57"><b>57)</b></a></sup> for the
2723 pointed-to type, the behavior is undefined. Otherwise, when converted back again, the
2724 result shall compare equal to the original pointer. When a pointer to an object is
2727 <!--page 60 -->
2728 converted to a pointer to a character type, the result points to the lowest addressed byte of
2729 the object. Successive increments of the result, up to the size of the object, yield pointers
2730 to the remaining bytes of the object.
2732 A pointer to a function of one type may be converted to a pointer to a function of another
2733 type and back again; the result shall compare equal to the original pointer. If a converted
2734 pointer is used to call a function whose type is not compatible with the pointed-to type,
2735 the behavior is undefined.
2736 <p><b> Forward references</b>: cast operators (<a href="#6.5.4">6.5.4</a>), equality operators (<a href="#6.5.9">6.5.9</a>), integer types
2737 capable of holding object pointers (<a href="#7.18.1.4">7.18.1.4</a>), simple assignment (<a href="#6.5.16.1">6.5.16.1</a>).
2738 <!--page 61 -->
2741 <p><small><a name="note55" href="#note55">55)</a> The macro NULL is defined in <a href="#7.17"><stddef.h></a> (and other headers) as a null pointer constant; see <a href="#7.17">7.17</a>.
2742 </small>
2743 <p><small><a name="note56" href="#note56">56)</a> The mapping functions for converting a pointer to an integer or an integer to a pointer are intended to
2744 be consistent with the addressing structure of the execution environment.
2745 </small>
2746 <p><small><a name="note57" href="#note57">57)</a> In general, the concept ''correctly aligned'' is transitive: if a pointer to type A is correctly aligned for a
2747 pointer to type B, which in turn is correctly aligned for a pointer to type C, then a pointer to type A is
2748 correctly aligned for a pointer to type C.
2749 </small>
2754 <pre>
2755 token:
2756 keyword
2757 identifier
2758 constant
2759 string-literal
2760 punctuator
2761 preprocessing-token:
2762 header-name
2763 identifier
2764 pp-number
2765 character-constant
2766 string-literal
2767 punctuator
2768 each non-white-space character that cannot be one of the above</pre>
2771 Each preprocessing token that is converted to a token shall have the lexical form of a
2772 keyword, an identifier, a constant, a string literal, or a punctuator.
2776 categories of tokens are: keywords, identifiers, constants, string literals, and punctuators.
2777 A preprocessing token is the minimal lexical element of the language in translation
2779 identifiers, preprocessing numbers, character constants, string literals, punctuators, and
2780 single non-white-space characters that do not lexically match the other preprocessing
2781 token categories.<sup><a href="#note58"><b>58)</b></a></sup> If a ' or a " character matches the last category, the behavior is
2782 undefined. Preprocessing tokens can be separated by white space; this consists of
2783 comments (described later), or white-space characters (space, horizontal tab, new-line,
2784 vertical tab, and form-feed), or both. As described in <a href="#6.10">6.10</a>, in certain circumstances
2785 during translation phase 4, white space (or the absence thereof) serves as more than
2786 preprocessing token separation. White space may appear within a preprocessing token
2787 only as part of a header name or between the quotation characters in a character constant
2788 or string literal.
2792 <!--page 62 -->
2793 <p><!--para 4 -->
2794 If the input stream has been parsed into preprocessing tokens up to a given character, the
2795 next preprocessing token is the longest sequence of characters that could constitute a
2796 preprocessing token. There is one exception to this rule: header name preprocessing
2797 tokens are recognized only within #include preprocessing directives and in
2798 implementation-defined locations within #pragma directives. In such contexts, a
2799 sequence of characters that could be either a header name or a string literal is recognized
2800 as the former.
2801 <p><!--para 5 -->
2802 EXAMPLE 1 The program fragment 1Ex is parsed as a preprocessing number token (one that is not a
2803 valid floating or integer constant token), even though a parse as the pair of preprocessing tokens 1 and Ex
2804 might produce a valid expression (for example, if Ex were a macro defined as +1). Similarly, the program
2805 fragment 1E1 is parsed as a preprocessing number (one that is a valid floating constant token), whether or
2806 not E is a macro name.
2808 <p><!--para 6 -->
2809 EXAMPLE 2 The program fragment x+++++y is parsed as x ++ ++ + y, which violates a constraint on
2810 increment operators, even though the parse x ++ + ++ y might yield a correct expression.
2812 <p><b> Forward references</b>: character constants (<a href="#6.4.4.4">6.4.4.4</a>), comments (<a href="#6.4.9">6.4.9</a>), expressions (<a href="#6.5">6.5</a>),
2813 floating constants (<a href="#6.4.4.2">6.4.4.2</a>), header names (<a href="#6.4.7">6.4.7</a>), macro replacement (<a href="#6.10.3">6.10.3</a>), postfix
2814 increment and decrement operators (<a href="#6.5.2.4">6.5.2.4</a>), prefix increment and decrement operators
2815 (<a href="#6.5.3.1">6.5.3.1</a>), preprocessing directives (<a href="#6.10">6.10</a>), preprocessing numbers (<a href="#6.4.8">6.4.8</a>), string literals
2818 <h6>footnotes</h6>
2819 <p><small><a name="note58" href="#note58">58)</a> An additional category, placemarkers, is used internally in translation phase 4 (see <a href="#6.10.3.3">6.10.3.3</a>); it cannot
2820 occur in source files.
2821 </small>
2824 <h6>Syntax</h6>
2825 <p><!--para 1 -->
2826 <pre>
2827 keyword: one of
2828 auto enum restrict unsigned
2829 break extern return void
2830 case float short volatile
2831 char for signed while
2832 const goto sizeof _Bool
2833 continue if static _Complex
2834 default inline struct _Imaginary
2835 do int switch
2836 double long typedef
2837 else register union</pre>
2838 <h6>Semantics</h6>
2839 <p><!--para 2 -->
2840 The above tokens (case sensitive) are reserved (in translation phases 7 and 8) for use as
2841 keywords, and shall not be used otherwise. The keyword _Imaginary is reserved for
2846 <!--page 63 -->
2848 <h6>footnotes</h6>
2849 <p><small><a name="note59" href="#note59">59)</a> One possible specification for imaginary types appears in <a href="#G">annex G</a>.
2850 </small>
2855 <h6>Syntax</h6>
2856 <p><!--para 1 -->
2857 <pre>
2858 identifier:
2859 identifier-nondigit
2860 identifier identifier-nondigit
2861 identifier digit
2862 identifier-nondigit:
2863 nondigit
2864 universal-character-name
2865 other implementation-defined characters
2866 nondigit: one of
2867 _ a b c d e f g h i j k l m
2868 n o p q r s t u v w x y z
2869 A B C D E F G H I J K L M
2870 N O P Q R S T U V W X Y Z
2871 digit: one of
2872 0 1 2 3 4 5 6 7 8 9</pre>
2873 <h6>Semantics</h6>
2874 <p><!--para 2 -->
2875 An identifier is a sequence of nondigit characters (including the underscore _, the
2876 lowercase and uppercase Latin letters, and other characters) and digits, which designates
2877 one or more entities as described in <a href="#6.2.1">6.2.1</a>. Lowercase and uppercase letters are distinct.
2878 There is no specific limit on the maximum length of an identifier.
2879 <p><!--para 3 -->
2880 Each universal character name in an identifier shall designate a character whose encoding
2881 in ISO/IEC 10646 falls into one of the ranges specified in <a href="#D">annex D</a>.<sup><a href="#note60"><b>60)</b></a></sup> The initial
2882 character shall not be a universal character name designating a digit. An implementation
2883 may allow multibyte characters that are not part of the basic source character set to
2884 appear in identifiers; which characters and their correspondence to universal character
2885 names is implementation-defined.
2886 <p><!--para 4 -->
2887 When preprocessing tokens are converted to tokens during translation phase 7, if a
2888 preprocessing token could be converted to either a keyword or an identifier, it is converted
2889 to a keyword.
2892 <!--page 64 -->
2893 Implementation limits
2894 <p><!--para 5 -->
2895 As discussed in <a href="#5.2.4.1">5.2.4.1</a>, an implementation may limit the number of significant initial
2896 characters in an identifier; the limit for an external name (an identifier that has external
2897 linkage) may be more restrictive than that for an internal name (a macro name or an
2898 identifier that does not have external linkage). The number of significant characters in an
2899 identifier is implementation-defined.
2900 <p><!--para 6 -->
2901 Any identifiers that differ in a significant character are different identifiers. If two
2902 identifiers differ only in nonsignificant characters, the behavior is undefined.
2903 <p><b> Forward references</b>: universal character names (<a href="#6.4.3">6.4.3</a>), macro replacement (<a href="#6.10.3">6.10.3</a>).
2905 <h6>footnotes</h6>
2906 <p><small><a name="note60" href="#note60">60)</a> On systems in which linkers cannot accept extended characters, an encoding of the universal character
2907 name may be used in forming valid external identifiers. For example, some otherwise unused
2908 character or sequence of characters may be used to encode the \u in a universal character name.
2909 Extended characters may produce a long external identifier.
2910 </small>
2913 <h6>Semantics</h6>
2914 <p><!--para 1 -->
2915 The identifier __func__ shall be implicitly declared by the translator as if,
2916 immediately following the opening brace of each function definition, the declaration
2917 <pre>
2919 appeared, where function-name is the name of the lexically-enclosing function.<sup><a href="#note61"><b>61)</b></a></sup>
2920 <p><!--para 2 -->
2921 This name is encoded as if the implicit declaration had been written in the source
2922 character set and then translated into the execution character set as indicated in translation
2923 phase 5.
2924 <p><!--para 3 -->
2925 EXAMPLE Consider the code fragment:
2926 <pre>
2928 void myfunc(void)
2929 {
2931 /* ... */
2932 }</pre>
2933 Each time the function is called, it will print to the standard output stream:
2934 <pre>
2935 myfunc</pre>
2942 <!--page 65 -->
2944 <h6>footnotes</h6>
2945 <p><small><a name="note61" href="#note61">61)</a> Since the name __func__ is reserved for any use by the implementation (<a href="#7.1.3">7.1.3</a>), if any other
2946 identifier is explicitly declared using the name __func__, the behavior is undefined.
2947 </small>
2950 <h6>Syntax</h6>
2951 <p><!--para 1 -->
2952 <pre>
2953 universal-character-name:
2954 \u hex-quad
2955 \U hex-quad hex-quad
2956 hex-quad:
2957 hexadecimal-digit hexadecimal-digit
2958 hexadecimal-digit hexadecimal-digit</pre>
2959 <h6>Constraints</h6>
2960 <p><!--para 2 -->
2961 A universal character name shall not specify a character whose short identifier is less than
2962 00A0 other than 0024 ($), 0040 (@), or 0060 ('), nor one in the range D800 through
2964 <h6>Description</h6>
2965 <p><!--para 3 -->
2966 Universal character names may be used in identifiers, character constants, and string
2967 literals to designate characters that are not in the basic character set.
2968 <h6>Semantics</h6>
2969 <p><!--para 4 -->
2970 The universal character name \Unnnnnnnn designates the character whose eight-digit
2971 short identifier (as specified by ISO/IEC 10646) is nnnnnnnn.<sup><a href="#note63"><b>63)</b></a></sup> Similarly, the universal
2972 character name \unnnn designates the character whose four-digit short identifier is nnnn
2973 (and whose eight-digit short identifier is 0000nnnn).
2978 <!--page 66 -->
2980 <h6>footnotes</h6>
2981 <p><small><a name="note62" href="#note62">62)</a> The disallowed characters are the characters in the basic character set and the code positions reserved
2982 by ISO/IEC 10646 for control characters, the character DELETE, and the S-zone (reserved for use by
2983 UTF-16).
2984 </small>
2985 <p><small><a name="note63" href="#note63">63)</a> Short identifiers for characters were first specified in ISO/IEC 10646-1/AMD9:1997.
2986 </small>
2989 <h6>Syntax</h6>
2990 <p><!--para 1 -->
2991 <pre>
2992 constant:
2993 integer-constant
2994 floating-constant
2995 enumeration-constant
2996 character-constant</pre>
2997 <h6>Constraints</h6>
2998 <p><!--para 2 -->
2999 Each constant shall have a type and the value of a constant shall be in the range of
3000 representable values for its type.
3001 <h6>Semantics</h6>
3002 <p><!--para 3 -->
3003 Each constant has a type, determined by its form and value, as detailed later.
3006 <h6>Syntax</h6>
3007 <p><!--para 1 -->
3008 <!--page 67 -->
3009 <pre>
3010 integer-constant:
3011 decimal-constant integer-suffixopt
3012 octal-constant integer-suffixopt
3013 hexadecimal-constant integer-suffixopt
3014 decimal-constant:
3015 nonzero-digit
3016 decimal-constant digit
3017 octal-constant:
3018 0
3019 octal-constant octal-digit
3020 hexadecimal-constant:
3021 hexadecimal-prefix hexadecimal-digit
3022 hexadecimal-constant hexadecimal-digit
3023 hexadecimal-prefix: one of
3024 0x 0X
3025 nonzero-digit: one of
3026 1 2 3 4 5 6 7 8 9
3027 octal-digit: one of
3028 0 1 2 3 4 5 6 7
3029 hexadecimal-digit: one of
3030 0 1 2 3 4 5 6 7 8 9
3031 a b c d e f
3032 A B C D E F
3033 integer-suffix:
3034 unsigned-suffix long-suffixopt
3035 unsigned-suffix long-long-suffix
3036 long-suffix unsigned-suffixopt
3037 long-long-suffix unsigned-suffixopt
3038 unsigned-suffix: one of
3039 u U
3040 long-suffix: one of
3041 l L
3042 long-long-suffix: one of
3043 ll LL</pre>
3044 <h6>Description</h6>
3045 <p><!--para 2 -->
3046 An integer constant begins with a digit, but has no period or exponent part. It may have a
3047 prefix that specifies its base and a suffix that specifies its type.
3048 <p><!--para 3 -->
3049 A decimal constant begins with a nonzero digit and consists of a sequence of decimal
3050 digits. An octal constant consists of the prefix 0 optionally followed by a sequence of the
3051 digits 0 through 7 only. A hexadecimal constant consists of the prefix 0x or 0X followed
3052 by a sequence of the decimal digits and the letters a (or A) through f (or F) with values
3053 10 through 15 respectively.
3054 <h6>Semantics</h6>
3055 <p><!--para 4 -->
3056 The value of a decimal constant is computed base 10; that of an octal constant, base 8;
3057 that of a hexadecimal constant, base 16. The lexically first digit is the most significant.
3058 <p><!--para 5 -->
3059 The type of an integer constant is the first of the corresponding list in which its value can
3060 be represented.
3061 <!--page 68 -->
3062 <pre>
3063 Octal or Hexadecimal</pre>
3064 Suffix Decimal Constant Constant
3066 none int int
3067 <pre>
3068 long int unsigned int
3069 long long int long int
3070 unsigned long int
3071 long long int
3072 unsigned long long int</pre>
3074 u or U unsigned int unsigned int
3075 <pre>
3076 unsigned long int unsigned long int
3077 unsigned long long int unsigned long long int</pre>
3079 l or L long int long int
3080 <pre>
3081 long long int unsigned long int
3082 long long int
3083 unsigned long long int</pre>
3085 Both u or U unsigned long int unsigned long int
3086 and l or L unsigned long long int unsigned long long int
3088 ll or LL long long int long long int
3089 <pre>
3090 unsigned long long int</pre>
3092 Both u or U unsigned long long int unsigned long long int
3093 and ll or LL
3094 <p><!--para 6 -->
3095 If an integer constant cannot be represented by any type in its list, it may have an
3096 extended integer type, if the extended integer type can represent its value. If all of the
3097 types in the list for the constant are signed, the extended integer type shall be signed. If
3098 all of the types in the list for the constant are unsigned, the extended integer type shall be
3099 unsigned. If the list contains both signed and unsigned types, the extended integer type
3100 may be signed or unsigned. If an integer constant cannot be represented by any type in
3101 its list and has no extended integer type, then the integer constant has no type.
3102 <!--page 69 -->
3105 <h6>Syntax</h6>
3106 <p><!--para 1 -->
3107 <!--page 70 -->
3108 <pre>
3109 floating-constant:
3110 decimal-floating-constant
3111 hexadecimal-floating-constant
3112 decimal-floating-constant:
3113 fractional-constant exponent-partopt floating-suffixopt
3114 digit-sequence exponent-part floating-suffixopt
3115 hexadecimal-floating-constant:
3116 hexadecimal-prefix hexadecimal-fractional-constant
3117 binary-exponent-part floating-suffixopt
3118 hexadecimal-prefix hexadecimal-digit-sequence
3119 binary-exponent-part floating-suffixopt
3120 fractional-constant:
3121 digit-sequenceopt . digit-sequence
3122 digit-sequence .
3123 exponent-part:
3124 e signopt digit-sequence
3125 E signopt digit-sequence
3126 sign: one of
3127 + -
3128 digit-sequence:
3129 digit
3130 digit-sequence digit
3131 hexadecimal-fractional-constant:
3132 hexadecimal-digit-sequenceopt .
3133 hexadecimal-digit-sequence
3134 hexadecimal-digit-sequence .
3135 binary-exponent-part:
3136 p signopt digit-sequence
3137 P signopt digit-sequence
3138 hexadecimal-digit-sequence:
3139 hexadecimal-digit
3140 hexadecimal-digit-sequence hexadecimal-digit
3141 floating-suffix: one of
3142 f l F L</pre>
3143 <h6>Description</h6>
3144 <p><!--para 2 -->
3145 A floating constant has a significand part that may be followed by an exponent part and a
3146 suffix that specifies its type. The components of the significand part may include a digit
3147 sequence representing the whole-number part, followed by a period (.), followed by a
3148 digit sequence representing the fraction part. The components of the exponent part are an
3149 e, E, p, or P followed by an exponent consisting of an optionally signed digit sequence.
3150 Either the whole-number part or the fraction part has to be present; for decimal floating
3151 constants, either the period or the exponent part has to be present.
3152 <h6>Semantics</h6>
3153 <p><!--para 3 -->
3154 The significand part is interpreted as a (decimal or hexadecimal) rational number; the
3155 digit sequence in the exponent part is interpreted as a decimal integer. For decimal
3156 floating constants, the exponent indicates the power of 10 by which the significand part is
3157 to be scaled. For hexadecimal floating constants, the exponent indicates the power of 2
3158 by which the significand part is to be scaled. For decimal floating constants, and also for
3159 hexadecimal floating constants when FLT_RADIX is not a power of 2, the result is either
3160 the nearest representable value, or the larger or smaller representable value immediately
3161 adjacent to the nearest representable value, chosen in an implementation-defined manner.
3162 For hexadecimal floating constants when FLT_RADIX is a power of 2, the result is
3163 correctly rounded.
3164 <p><!--para 4 -->
3165 An unsuffixed floating constant has type double. If suffixed by the letter f or F, it has
3166 type float. If suffixed by the letter l or L, it has type long double.
3167 <p><!--para 5 -->
3168 Floating constants are converted to internal format as if at translation-time. The
3169 conversion of a floating constant shall not raise an exceptional condition or a floating-
3170 point exception at execution time.
3171 Recommended practice
3172 <p><!--para 6 -->
3173 The implementation should produce a diagnostic message if a hexadecimal constant
3174 cannot be represented exactly in its evaluation format; the implementation should then
3175 proceed with the translation of the program.
3176 <p><!--para 7 -->
3177 The translation-time conversion of floating constants should match the execution-time
3178 conversion of character strings by library functions, such as strtod, given matching
3179 inputs suitable for both conversions, the same result format, and default execution-time
3185 <!--page 71 -->
3187 <h6>footnotes</h6>
3188 <p><small><a name="note64" href="#note64">64)</a> The specification for the library functions recommends more accurate conversion than required for
3190 </small>
3193 <h6>Syntax</h6>
3194 <p><!--para 1 -->
3195 <pre>
3196 enumeration-constant:
3197 identifier</pre>
3198 <h6>Semantics</h6>
3199 <p><!--para 2 -->
3200 An identifier declared as an enumeration constant has type int.
3204 <h6>Syntax</h6>
3205 <p><!--para 1 -->
3206 <!--page 72 -->
3207 <pre>
3208 character-constant:
3209 ' c-char-sequence '
3210 L' c-char-sequence '
3211 c-char-sequence:
3212 c-char
3213 c-char-sequence c-char
3214 c-char:
3215 any member of the source character set except
3216 the single-quote ', backslash \, or new-line character
3217 escape-sequence
3218 escape-sequence:
3219 simple-escape-sequence
3220 octal-escape-sequence
3221 hexadecimal-escape-sequence
3222 universal-character-name
3223 simple-escape-sequence: one of
3224 \' \" \? \\
3225 \a \b \f \n \r \t \v
3226 octal-escape-sequence:
3227 \ octal-digit
3228 \ octal-digit octal-digit
3229 \ octal-digit octal-digit octal-digit
3230 hexadecimal-escape-sequence:
3231 \x hexadecimal-digit
3232 hexadecimal-escape-sequence hexadecimal-digit</pre>
3235 An integer character constant is a sequence of one or more multibyte characters enclosed
3236 in single-quotes, as in 'x'. A wide character constant is the same, except prefixed by the
3237 letter L. With a few exceptions detailed later, the elements of the sequence are any
3238 members of the source character set; they are mapped in an implementation-defined
3239 manner to members of the execution character set.
3241 The single-quote ', the double-quote ", the question-mark ?, the backslash \, and
3242 arbitrary integer values are representable according to the following table of escape
3243 sequences:
3244 <p><!--para 4 -->
3245 <pre>
3246 single quote ' \'
3248 question mark ? \?
3249 backslash \ \\
3250 octal character \octal digits
3251 hexadecimal character \x hexadecimal digits</pre>
3252 The double-quote " and question-mark ? are representable either by themselves or by the
3253 escape sequences \" and \?, respectively, but the single-quote ' and the backslash \
3254 shall be represented, respectively, by the escape sequences \' and \\.
3255 <p><!--para 5 -->
3256 The octal digits that follow the backslash in an octal escape sequence are taken to be part
3257 of the construction of a single character for an integer character constant or of a single
3258 wide character for a wide character constant. The numerical value of the octal integer so
3259 formed specifies the value of the desired character or wide character.
3260 <p><!--para 6 -->
3261 The hexadecimal digits that follow the backslash and the letter x in a hexadecimal escape
3262 sequence are taken to be part of the construction of a single character for an integer
3263 character constant or of a single wide character for a wide character constant. The
3264 numerical value of the hexadecimal integer so formed specifies the value of the desired
3265 character or wide character.
3266 <p><!--para 7 -->
3267 Each octal or hexadecimal escape sequence is the longest sequence of characters that can
3268 constitute the escape sequence.
3269 <p><!--para 8 -->
3270 In addition, characters not in the basic character set are representable by universal
3271 character names and certain nongraphic characters are representable by escape sequences
3272 consisting of the backslash \ followed by a lowercase letter: \a, \b, \f, \n, \r, \t,
3278 <!--page 73 -->
3279 <h6>Constraints</h6>
3280 <p><!--para 9 -->
3281 The value of an octal or hexadecimal escape sequence shall be in the range of
3282 representable values for the type unsigned char for an integer character constant, or
3283 the unsigned type corresponding to wchar_t for a wide character constant.
3284 <h6>Semantics</h6>
3285 <p><!--para 10 -->
3286 An integer character constant has type int. The value of an integer character constant
3287 containing a single character that maps to a single-byte execution character is the
3288 numerical value of the representation of the mapped character interpreted as an integer.
3289 The value of an integer character constant containing more than one character (e.g.,
3290 'ab'), or containing a character or escape sequence that does not map to a single-byte
3291 execution character, is implementation-defined. If an integer character constant contains
3292 a single character or escape sequence, its value is the one that results when an object with
3293 type char whose value is that of the single character or escape sequence is converted to
3294 type int.
3295 <p><!--para 11 -->
3296 A wide character constant has type wchar_t, an integer type defined in the
3297 <a href="#7.17"><stddef.h></a> header. The value of a wide character constant containing a single
3298 multibyte character that maps to a member of the extended execution character set is the
3299 wide character corresponding to that multibyte character, as defined by the mbtowc
3300 function, with an implementation-defined current locale. The value of a wide character
3301 constant containing more than one multibyte character, or containing a multibyte
3302 character or escape sequence not represented in the extended execution character set, is
3303 implementation-defined.
3304 <p><!--para 12 -->
3305 EXAMPLE 1 The construction '\0' is commonly used to represent the null character.
3307 <p><!--para 13 -->
3308 EXAMPLE 2 Consider implementations that use two's-complement representation for integers and eight
3309 bits for objects that have type char. In an implementation in which type char has the same range of
3310 values as signed char, the integer character constant '\xFF' has the value -1; if type char has the
3311 same range of values as unsigned char, the character constant '\xFF' has the value +255.
3313 <p><!--para 14 -->
3314 EXAMPLE 3 Even if eight bits are used for objects that have type char, the construction '\x123'
3315 specifies an integer character constant containing only one character, since a hexadecimal escape sequence
3316 is terminated only by a non-hexadecimal character. To specify an integer character constant containing the
3317 two characters whose values are '\x12' and '3', the construction '\0223' may be used, since an octal
3318 escape sequence is terminated after three octal digits. (The value of this two-character integer character
3319 constant is implementation-defined.)
3321 <p><!--para 15 -->
3322 EXAMPLE 4 Even if 12 or more bits are used for objects that have type wchar_t, the construction
3323 L'\1234' specifies the implementation-defined value that results from the combination of the values
3324 0123 and '4'.
3326 <p><b> Forward references</b>: common definitions <a href="#7.17"><stddef.h></a> (<a href="#7.17">7.17</a>), the mbtowc function
3328 <!--page 74 -->
3330 <h6>footnotes</h6>
3331 <p><small><a name="note65" href="#note65">65)</a> The semantics of these characters were discussed in <a href="#5.2.2">5.2.2</a>. If any other character follows a backslash,
3332 the result is not a token and a diagnostic is required. See ''future language directions'' (<a href="#6.11.4">6.11.4</a>).
3333 </small>
3336 <h6>Syntax</h6>
3337 <p><!--para 1 -->
3338 <pre>
3339 string-literal:
3342 s-char-sequence:
3343 s-char
3344 s-char-sequence s-char
3345 s-char:
3346 any member of the source character set except
3347 the double-quote ", backslash \, or new-line character
3348 escape-sequence</pre>
3351 A character string literal is a sequence of zero or more multibyte characters enclosed in
3352 double-quotes, as in "xyz". A wide string literal is the same, except prefixed by the
3353 letter L.
3355 The same considerations apply to each element of the sequence in a character string
3356 literal or a wide string literal as if it were in an integer character constant or a wide
3357 character constant, except that the single-quote ' is representable either by itself or by the
3358 escape sequence \', but the double-quote " shall be represented by the escape sequence
3359 \".
3362 In translation phase 6, the multibyte character sequences specified by any sequence of
3363 adjacent character and wide string literal tokens are concatenated into a single multibyte
3364 character sequence. If any of the tokens are wide string literal tokens, the resulting
3365 multibyte character sequence is treated as a wide string literal; otherwise, it is treated as a
3366 character string literal.
3368 In translation phase 7, a byte or code of value zero is appended to each multibyte
3369 character sequence that results from a string literal or literals.<sup><a href="#note66"><b>66)</b></a></sup> The multibyte character
3370 sequence is then used to initialize an array of static storage duration and length just
3371 sufficient to contain the sequence. For character string literals, the array elements have
3372 type char, and are initialized with the individual bytes of the multibyte character
3373 sequence; for wide string literals, the array elements have type wchar_t, and are
3374 initialized with the sequence of wide characters corresponding to the multibyte character
3376 <!--page 75 -->
3377 sequence, as defined by the mbstowcs function with an implementation-defined current
3378 locale. The value of a string literal containing a multibyte character or escape sequence
3379 not represented in the execution character set is implementation-defined.
3381 It is unspecified whether these arrays are distinct provided their elements have the
3382 appropriate values. If the program attempts to modify such an array, the behavior is
3383 undefined.
3385 EXAMPLE This pair of adjacent character string literals
3386 <pre>
3388 produces a single character string literal containing the two characters whose values are '\x12' and '3',
3389 because escape sequences are converted into single members of the execution character set just prior to
3390 adjacent string literal concatenation.
3392 <p><b> Forward references</b>: common definitions <a href="#7.17"><stddef.h></a> (<a href="#7.17">7.17</a>), the mbstowcs
3396 <p><small><a name="note66" href="#note66">66)</a> A character string literal need not be a string (see <a href="#7.1.1">7.1.1</a>), because a null character may be embedded in
3397 it by a \0 escape sequence.
3398 </small>
3403 <pre>
3404 punctuator: one of
3405 [ ] ( ) { } . ->
3406 ++ -- & * + - ~ !
3408 ? : ; ...
3410 , # ##
3414 A punctuator is a symbol that has independent syntactic and semantic significance.
3415 Depending on context, it may specify an operation to be performed (which in turn may
3416 yield a value or a function designator, produce a side effect, or some combination thereof)
3417 in which case it is known as an operator (other forms of operator also exist in some
3418 contexts). An operand is an entity on which an operator acts.
3419 <!--page 76 -->
3422 <pre>
3424 behave, respectively, the same as the six tokens
3425 <pre>
3426 [ ] { } # ##</pre>
3428 <p><b> Forward references</b>: expressions (<a href="#6.5">6.5</a>), declarations (<a href="#6.7">6.7</a>), preprocessing directives
3432 <p><small><a name="note67" href="#note67">67)</a> These tokens are sometimes called ''digraphs''.
3433 </small>
3434 <p><small><a name="note68" href="#note68">68)</a> Thus [ and <: behave differently when ''stringized'' (see <a href="#6.10.3.2">6.10.3.2</a>), but can otherwise be freely
3435 interchanged.
3436 </small>
3441 <pre>
3442 header-name:
3444 " q-char-sequence "
3445 h-char-sequence:
3446 h-char
3447 h-char-sequence h-char
3448 h-char:
3449 any member of the source character set except
3450 the new-line character and >
3451 q-char-sequence:
3452 q-char
3453 q-char-sequence q-char
3454 q-char:
3455 any member of the source character set except
3456 the new-line character and "</pre>
3457 <h6>Semantics</h6>
3458 <p><!--para 2 -->
3459 The sequences in both forms of header names are mapped in an implementation-defined
3461 <p><!--para 3 -->
3462 If the characters ', \, ", //, or /* occur in the sequence between the < and > delimiters,
3463 the behavior is undefined. Similarly, if the characters ', \, //, or /* occur in the
3468 <!--page 77 -->
3469 sequence between the " delimiters, the behavior is undefined.<sup><a href="#note69"><b>69)</b></a></sup> Header name
3470 preprocessing tokens are recognized only within #include preprocessing directives and
3471 in implementation-defined locations within #pragma directives.<sup><a href="#note70"><b>70)</b></a></sup>
3472 <p><!--para 4 -->
3473 EXAMPLE The following sequence of characters:
3474 <pre>
3475 0x3<1/a.h>1e2
3476 #include <1/a.h>
3477 #define const.member@$</pre>
3478 forms the following sequence of preprocessing tokens (with each individual preprocessing token delimited
3479 by a { on the left and a } on the right).
3480 <pre>
3481 {0x3}{<}{1}{/}{a}{.}{h}{>}{1e2}
3482 {#}{include} {<1/a.h>}
3483 {#}{define} {const}{.}{member}{@}{$}</pre>
3487 <h6>footnotes</h6>
3488 <p><small><a name="note69" href="#note69">69)</a> Thus, sequences of characters that resemble escape sequences cause undefined behavior.
3489 </small>
3490 <p><small><a name="note70" href="#note70">70)</a> For an example of a header name preprocessing token used in a #pragma directive, see <a href="#6.10.9">6.10.9</a>.
3491 </small>
3494 <h6>Syntax</h6>
3495 <p><!--para 1 -->
3496 <pre>
3497 pp-number:
3498 digit
3499 . digit
3500 pp-number digit
3501 pp-number identifier-nondigit
3502 pp-number e sign
3503 pp-number E sign
3504 pp-number p sign
3505 pp-number P sign
3506 pp-number .</pre>
3507 <h6>Description</h6>
3508 <p><!--para 2 -->
3509 A preprocessing number begins with a digit optionally preceded by a period (.) and may
3510 be followed by valid identifier characters and the character sequences e+, e-, E+, E-,
3511 p+, p-, P+, or P-.
3512 <p><!--para 3 -->
3513 Preprocessing number tokens lexically include all floating and integer constant tokens.
3514 <h6>Semantics</h6>
3515 <p><!--para 4 -->
3516 A preprocessing number does not have type or a value; it acquires both after a successful
3517 conversion (as part of translation phase 7) to a floating constant token or an integer
3518 constant token.
3521 <!--page 78 -->
3524 <p><!--para 1 -->
3525 Except within a character constant, a string literal, or a comment, the characters /*
3526 introduce a comment. The contents of such a comment are examined only to identify
3527 multibyte characters and to find the characters */ that terminate it.<sup><a href="#note71"><b>71)</b></a></sup>
3528 <p><!--para 2 -->
3529 Except within a character constant, a string literal, or a comment, the characters //
3530 introduce a comment that includes all multibyte characters up to, but not including, the
3531 next new-line character. The contents of such a comment are examined only to identify
3532 multibyte characters and to find the terminating new-line character.
3533 <p><!--para 3 -->
3534 EXAMPLE
3535 <pre>
3538 // */ // comment, not syntax error
3539 f = g/**//h; // equivalent to f = g / h;
3540 //\
3541 i(); // part of a two-line comment
3542 /\
3543 / j(); // part of a two-line comment
3544 #define glue(x,y) x##y
3545 glue(/,/) k(); // syntax error, not comment
3546 /*//*/ l(); // equivalent to l();
3547 m = n//**/o
3548 + p; // equivalent to m = n + p;</pre>
3553 <!--page 79 -->
3555 <h6>footnotes</h6>
3557 </small>
3560 <p><!--para 1 -->
3561 An expression is a sequence of operators and operands that specifies computation of a
3562 value, or that designates an object or a function, or that generates side effects, or that
3563 performs a combination thereof.
3564 <p><!--para 2 -->
3565 Between the previous and next sequence point an object shall have its stored value
3566 modified at most once by the evaluation of an expression.<sup><a href="#note72"><b>72)</b></a></sup> Furthermore, the prior value
3567 shall be read only to determine the value to be stored.<sup><a href="#note73"><b>73)</b></a></sup>
3568 <p><!--para 3 -->
3569 The grouping of operators and operands is indicated by the syntax.<sup><a href="#note74"><b>74)</b></a></sup> Except as specified
3570 later (for the function-call (), &&, ||, ?:, and comma operators), the order of evaluation
3571 of subexpressions and the order in which side effects take place are both unspecified.
3572 <p><!--para 4 -->
3573 Some operators (the unary operator ~, and the binary operators <<, >>, &, ^, and |,
3574 collectively described as bitwise operators) are required to have operands that have
3575 integer type. These operators yield values that depend on the internal representations of
3576 integers, and have implementation-defined and undefined aspects for signed types.
3577 <p><!--para 5 -->
3578 If an exceptional condition occurs during the evaluation of an expression (that is, if the
3579 result is not mathematically defined or not in the range of representable values for its
3580 type), the behavior is undefined.
3581 <p><!--para 6 -->
3582 The effective type of an object for an access to its stored value is the declared type of the
3583 object, if any.<sup><a href="#note75"><b>75)</b></a></sup> If a value is stored into an object having no declared type through an
3584 lvalue having a type that is not a character type, then the type of the lvalue becomes the
3587 <!--page 80 -->
3588 effective type of the object for that access and for subsequent accesses that do not modify
3589 the stored value. If a value is copied into an object having no declared type using
3590 memcpy or memmove, or is copied as an array of character type, then the effective type
3591 of the modified object for that access and for subsequent accesses that do not modify the
3592 value is the effective type of the object from which the value is copied, if it has one. For
3593 all other accesses to an object having no declared type, the effective type of the object is
3594 simply the type of the lvalue used for the access.
3595 <p><!--para 7 -->
3596 An object shall have its stored value accessed only by an lvalue expression that has one of
3598 <ul>
3599 <li> a type compatible with the effective type of the object,
3600 <li> a qualified version of a type compatible with the effective type of the object,
3601 <li> a type that is the signed or unsigned type corresponding to the effective type of the
3602 object,
3603 <li> a type that is the signed or unsigned type corresponding to a qualified version of the
3604 effective type of the object,
3605 <li> an aggregate or union type that includes one of the aforementioned types among its
3606 members (including, recursively, a member of a subaggregate or contained union), or
3607 <li> a character type.
3608 </ul>
3609 <p><!--para 8 -->
3610 A floating expression may be contracted, that is, evaluated as though it were an atomic
3611 operation, thereby omitting rounding errors implied by the source code and the
3612 expression evaluation method.<sup><a href="#note77"><b>77)</b></a></sup> The FP_CONTRACT pragma in <a href="#7.12"><math.h></a> provides a
3613 way to disallow contracted expressions. Otherwise, whether and how expressions are
3615 <p><b> Forward references</b>: the FP_CONTRACT pragma (<a href="#7.12.2">7.12.2</a>), copying functions (<a href="#7.21.2">7.21.2</a>).
3620 <!--page 81 -->
3622 <h6>footnotes</h6>
3623 <p><small><a name="note72" href="#note72">72)</a> A floating-point status flag is not an object and can be set more than once within an expression.
3624 </small>
3625 <p><small><a name="note73" href="#note73">73)</a> This paragraph renders undefined statement expressions such as
3627 <pre>
3628 i = ++i + 1;
3629 a[i++] = i;
3630 while allowing
3631 i = i + 1;
3632 a[i] = i;</pre>
3634 </small>
3635 <p><small><a name="note74" href="#note74">74)</a> The syntax specifies the precedence of operators in the evaluation of an expression, which is the same
3636 as the order of the major subclauses of this subclause, highest precedence first. Thus, for example, the
3637 expressions allowed as the operands of the binary + operator (<a href="#6.5.6">6.5.6</a>) are those expressions defined in
3638 <a href="#6.5.1">6.5.1</a> through <a href="#6.5.6">6.5.6</a>. The exceptions are cast expressions (<a href="#6.5.4">6.5.4</a>) as operands of unary operators
3639 (<a href="#6.5.3">6.5.3</a>), and an operand contained between any of the following pairs of operators: grouping
3640 parentheses () (<a href="#6.5.1">6.5.1</a>), subscripting brackets [] (<a href="#6.5.2.1">6.5.2.1</a>), function-call parentheses () (<a href="#6.5.2.2">6.5.2.2</a>), and
3643 <pre>
3644 Within each major subclause, the operators have the same precedence. Left- or right-associativity is
3645 indicated in each subclause by the syntax for the expressions discussed therein.</pre>
3646 </small>
3648 </small>
3649 <p><small><a name="note76" href="#note76">76)</a> The intent of this list is to specify those circumstances in which an object may or may not be aliased.
3650 </small>
3651 <p><small><a name="note77" href="#note77">77)</a> A contracted expression might also omit the raising of floating-point exceptions.
3652 </small>
3653 <p><small><a name="note78" href="#note78">78)</a> This license is specifically intended to allow implementations to exploit fast machine instructions that
3654 combine multiple C operators. As contractions potentially undermine predictability, and can even
3655 decrease accuracy for containing expressions, their use needs to be well-defined and clearly
3656 documented.
3657 </small>
3660 <h6>Syntax</h6>
3661 <p><!--para 1 -->
3662 <pre>
3663 primary-expression:
3664 identifier
3665 constant
3666 string-literal
3667 ( expression )</pre>
3668 <h6>Semantics</h6>
3669 <p><!--para 2 -->
3670 An identifier is a primary expression, provided it has been declared as designating an
3671 object (in which case it is an lvalue) or a function (in which case it is a function
3673 <p><!--para 3 -->
3674 A constant is a primary expression. Its type depends on its form and value, as detailed in
3676 <p><!--para 4 -->
3677 A string literal is a primary expression. It is an lvalue with type as detailed in <a href="#6.4.5">6.4.5</a>.
3678 <p><!--para 5 -->
3679 A parenthesized expression is a primary expression. Its type and value are identical to
3680 those of the unparenthesized expression. It is an lvalue, a function designator, or a void
3681 expression if the unparenthesized expression is, respectively, an lvalue, a function
3682 designator, or a void expression.
3685 <h6>footnotes</h6>
3686 <p><small><a name="note79" href="#note79">79)</a> Thus, an undeclared identifier is a violation of the syntax.
3687 </small>
3690 <h6>Syntax</h6>
3691 <p><!--para 1 -->
3692 <pre>
3693 postfix-expression:
3694 primary-expression
3695 postfix-expression [ expression ]
3696 postfix-expression ( argument-expression-listopt )
3697 postfix-expression . identifier
3698 postfix-expression -> identifier
3699 postfix-expression ++
3700 postfix-expression --
3701 ( type-name ) { initializer-list }
3702 ( type-name ) { initializer-list , }</pre>
3707 <!--page 82 -->
3708 <pre>
3709 argument-expression-list:
3710 assignment-expression
3711 argument-expression-list , assignment-expression</pre>
3714 <h6>Constraints</h6>
3715 <p><!--para 1 -->
3716 One of the expressions shall have type ''pointer to object type'', the other expression shall
3717 have integer type, and the result has type ''type''.
3718 <h6>Semantics</h6>
3719 <p><!--para 2 -->
3720 A postfix expression followed by an expression in square brackets [] is a subscripted
3721 designation of an element of an array object. The definition of the subscript operator []
3722 is that E1[E2] is identical to (*((E1)+(E2))). Because of the conversion rules that
3723 apply to the binary + operator, if E1 is an array object (equivalently, a pointer to the
3724 initial element of an array object) and E2 is an integer, E1[E2] designates the E2-th
3725 element of E1 (counting from zero).
3726 <p><!--para 3 -->
3727 Successive subscript operators designate an element of a multidimensional array object.
3728 If E is an n-dimensional array (n >= 2) with dimensions i x j x . . . x k, then E (used as
3729 other than an lvalue) is converted to a pointer to an (n - 1)-dimensional array with
3730 dimensions j x . . . x k. If the unary * operator is applied to this pointer explicitly, or
3731 implicitly as a result of subscripting, the result is the pointed-to (n - 1)-dimensional array,
3732 which itself is converted into a pointer if used as other than an lvalue. It follows from this
3733 that arrays are stored in row-major order (last subscript varies fastest).
3734 <p><!--para 4 -->
3735 EXAMPLE Consider the array object defined by the declaration
3736 <pre>
3737 int x[3][5];</pre>
3738 Here x is a 3 x 5 array of ints; more precisely, x is an array of three element objects, each of which is an
3739 array of five ints. In the expression x[i], which is equivalent to (*((x)+(i))), x is first converted to
3740 a pointer to the initial array of five ints. Then i is adjusted according to the type of x, which conceptually
3741 entails multiplying i by the size of the object to which the pointer points, namely an array of five int
3742 objects. The results are added and indirection is applied to yield an array of five ints. When used in the
3743 expression x[i][j], that array is in turn converted to a pointer to the first of the ints, so x[i][j]
3744 yields an int.
3746 <p><b> Forward references</b>: additive operators (<a href="#6.5.6">6.5.6</a>), address and indirection operators
3748 <!--page 83 -->
3751 <h6>Constraints</h6>
3752 <p><!--para 1 -->
3753 The expression that denotes the called function<sup><a href="#note80"><b>80)</b></a></sup> shall have type pointer to function
3754 returning void or returning an object type other than an array type.
3755 <p><!--para 2 -->
3756 If the expression that denotes the called function has a type that includes a prototype, the
3757 number of arguments shall agree with the number of parameters. Each argument shall
3758 have a type such that its value may be assigned to an object with the unqualified version
3759 of the type of its corresponding parameter.
3760 <h6>Semantics</h6>
3761 <p><!--para 3 -->
3762 A postfix expression followed by parentheses () containing a possibly empty, comma-
3763 separated list of expressions is a function call. The postfix expression denotes the called
3764 function. The list of expressions specifies the arguments to the function.
3765 <p><!--para 4 -->
3766 An argument may be an expression of any object type. In preparing for the call to a
3767 function, the arguments are evaluated, and each parameter is assigned the value of the
3769 <p><!--para 5 -->
3770 If the expression that denotes the called function has type pointer to function returning an
3771 object type, the function call expression has the same type as that object type, and has the
3772 value determined as specified in <a href="#6.8.6.4">6.8.6.4</a>. Otherwise, the function call has type void. If
3773 an attempt is made to modify the result of a function call or to access it after the next
3774 sequence point, the behavior is undefined.
3775 <p><!--para 6 -->
3776 If the expression that denotes the called function has a type that does not include a
3777 prototype, the integer promotions are performed on each argument, and arguments that
3778 have type float are promoted to double. These are called the default argument
3779 promotions. If the number of arguments does not equal the number of parameters, the
3780 behavior is undefined. If the function is defined with a type that includes a prototype, and
3781 either the prototype ends with an ellipsis (, ...) or the types of the arguments after
3782 promotion are not compatible with the types of the parameters, the behavior is undefined.
3783 If the function is defined with a type that does not include a prototype, and the types of
3784 the arguments after promotion are not compatible with those of the parameters after
3785 promotion, the behavior is undefined, except for the following cases:
3790 <!--page 84 -->
3791 <ul>
3792 <li> one promoted type is a signed integer type, the other promoted type is the
3793 corresponding unsigned integer type, and the value is representable in both types;
3794 <li> both types are pointers to qualified or unqualified versions of a character type or
3795 void.
3796 </ul>
3797 <p><!--para 7 -->
3798 If the expression that denotes the called function has a type that does include a prototype,
3799 the arguments are implicitly converted, as if by assignment, to the types of the
3800 corresponding parameters, taking the type of each parameter to be the unqualified version
3801 of its declared type. The ellipsis notation in a function prototype declarator causes
3802 argument type conversion to stop after the last declared parameter. The default argument
3803 promotions are performed on trailing arguments.
3804 <p><!--para 8 -->
3805 No other conversions are performed implicitly; in particular, the number and types of
3806 arguments are not compared with those of the parameters in a function definition that
3807 does not include a function prototype declarator.
3808 <p><!--para 9 -->
3809 If the function is defined with a type that is not compatible with the type (of the
3810 expression) pointed to by the expression that denotes the called function, the behavior is
3811 undefined.
3812 <p><!--para 10 -->
3813 The order of evaluation of the function designator, the actual arguments, and
3814 subexpressions within the actual arguments is unspecified, but there is a sequence point
3815 before the actual call.
3816 <p><!--para 11 -->
3817 Recursive function calls shall be permitted, both directly and indirectly through any chain
3818 of other functions.
3819 <p><!--para 12 -->
3820 EXAMPLE In the function call
3821 <pre>
3822 (*pf[f1()]) (f2(), f3() + f4())</pre>
3823 the functions f1, f2, f3, and f4 may be called in any order. All side effects have to be completed before
3824 the function pointed to by pf[f1()] is called.
3826 <p><b> Forward references</b>: function declarators (including prototypes) (<a href="#6.7.5.3">6.7.5.3</a>), function
3827 definitions (<a href="#6.9.1">6.9.1</a>), the return statement (<a href="#6.8.6.4">6.8.6.4</a>), simple assignment (<a href="#6.5.16.1">6.5.16.1</a>).
3829 <h6>footnotes</h6>
3830 <p><small><a name="note80" href="#note80">80)</a> Most often, this is the result of converting an identifier that is a function designator.
3831 </small>
3832 <p><small><a name="note81" href="#note81">81)</a> A function may change the values of its parameters, but these changes cannot affect the values of the
3833 arguments. On the other hand, it is possible to pass a pointer to an object, and the function may
3834 change the value of the object pointed to. A parameter declared to have array or function type is
3836 </small>
3839 <h6>Constraints</h6>
3840 <p><!--para 1 -->
3841 The first operand of the . operator shall have a qualified or unqualified structure or union
3842 type, and the second operand shall name a member of that type.
3843 <p><!--para 2 -->
3844 The first operand of the -> operator shall have type ''pointer to qualified or unqualified
3845 structure'' or ''pointer to qualified or unqualified union'', and the second operand shall
3846 name a member of the type pointed to.
3847 <!--page 85 -->
3848 <h6>Semantics</h6>
3849 <p><!--para 3 -->
3850 A postfix expression followed by the . operator and an identifier designates a member of
3851 a structure or union object. The value is that of the named member,<sup><a href="#note82"><b>82)</b></a></sup> and is an lvalue if
3852 the first expression is an lvalue. If the first expression has qualified type, the result has
3853 the so-qualified version of the type of the designated member.
3854 <p><!--para 4 -->
3855 A postfix expression followed by the -> operator and an identifier designates a member
3856 of a structure or union object. The value is that of the named member of the object to
3857 which the first expression points, and is an lvalue.<sup><a href="#note83"><b>83)</b></a></sup> If the first expression is a pointer to
3858 a qualified type, the result has the so-qualified version of the type of the designated
3859 member.
3860 <p><!--para 5 -->
3861 One special guarantee is made in order to simplify the use of unions: if a union contains
3862 several structures that share a common initial sequence (see below), and if the union
3863 object currently contains one of these structures, it is permitted to inspect the common
3864 initial part of any of them anywhere that a declaration of the complete type of the union is
3865 visible. Two structures share a common initial sequence if corresponding members have
3866 compatible types (and, for bit-fields, the same widths) for a sequence of one or more
3867 initial members.
3868 <p><!--para 6 -->
3869 EXAMPLE 1 If f is a function returning a structure or union, and x is a member of that structure or
3870 union, f().x is a valid postfix expression but is not an lvalue.
3872 <p><!--para 7 -->
3873 EXAMPLE 2 In:
3874 <pre>
3875 struct s { int i; const int ci; };
3876 struct s s;
3877 const struct s cs;
3878 volatile struct s vs;</pre>
3879 the various members have the types:
3880 <pre>
3881 s.i int
3882 s.ci const int
3883 cs.i const int
3884 cs.ci const int
3885 vs.i volatile int
3886 vs.ci volatile const int</pre>
3891 <!--page 86 -->
3892 <p><!--para 8 -->
3893 EXAMPLE 3 The following is a valid fragment:
3894 <pre>
3895 union {
3896 struct {
3897 int alltypes;
3898 } n;
3899 struct {
3900 int type;
3901 int intnode;
3902 } ni;
3903 struct {
3904 int type;
3905 double doublenode;
3906 } nf;
3907 } u;
3908 u.nf.type = 1;
3910 /* ... */
3911 if (u.n.alltypes == 1)
3912 if (sin(u.nf.doublenode) == 0.0)
3913 /* ... */</pre>
3914 The following is not a valid fragment (because the union type is not visible within function f):
3915 <pre>
3916 struct t1 { int m; };
3917 struct t2 { int m; };
3918 int f(struct t1 *p1, struct t2 *p2)
3919 {
3920 if (p1->m < 0)
3921 p2->m = -p2->m;
3922 return p1->m;
3923 }
3924 int g()
3925 {
3926 union {
3927 struct t1 s1;
3928 struct t2 s2;
3929 } u;
3930 /* ... */
3931 return f(&u.s1, &u.s2);
3932 }</pre>
3934 <p><b> Forward references</b>: address and indirection operators (<a href="#6.5.3.2">6.5.3.2</a>), structure and union
3936 <!--page 87 -->
3938 <h6>footnotes</h6>
3939 <p><small><a name="note82" href="#note82">82)</a> If the member used to access the contents of a union object is not the same as the member last used to
3940 store a value in the object, the appropriate part of the object representation of the value is reinterpreted
3941 as an object representation in the new type as described in <a href="#6.2.6">6.2.6</a> (a process sometimes called "type
3942 punning"). This might be a trap representation.
3943 </small>
3944 <p><small><a name="note83" href="#note83">83)</a> If &E is a valid pointer expression (where & is the ''address-of '' operator, which generates a pointer to
3945 its operand), the expression (&E)->MOS is the same as E.MOS.
3946 </small>
3948 <h5><a name="6.5.2.4" href="#6.5.2.4">6.5.2.4 Postfix increment and decrement operators</a></h5>
3949 <h6>Constraints</h6>
3950 <p><!--para 1 -->
3951 The operand of the postfix increment or decrement operator shall have qualified or
3952 unqualified real or pointer type and shall be a modifiable lvalue.
3953 <h6>Semantics</h6>
3954 <p><!--para 2 -->
3955 The result of the postfix ++ operator is the value of the operand. After the result is
3956 obtained, the value of the operand is incremented. (That is, the value 1 of the appropriate
3957 type is added to it.) See the discussions of additive operators and compound assignment
3958 for information on constraints, types, and conversions and the effects of operations on
3959 pointers. The side effect of updating the stored value of the operand shall occur between
3960 the previous and the next sequence point.
3961 <p><!--para 3 -->
3962 The postfix -- operator is analogous to the postfix ++ operator, except that the value of
3963 the operand is decremented (that is, the value 1 of the appropriate type is subtracted from
3964 it).
3965 <p><b> Forward references</b>: additive operators (<a href="#6.5.6">6.5.6</a>), compound assignment (<a href="#6.5.16.2">6.5.16.2</a>).
3968 <h6>Constraints</h6>
3969 <p><!--para 1 -->
3970 The type name shall specify an object type or an array of unknown size, but not a variable
3971 length array type.
3972 <p><!--para 2 -->
3973 No initializer shall attempt to provide a value for an object not contained within the entire
3974 unnamed object specified by the compound literal.
3975 <p><!--para 3 -->
3976 If the compound literal occurs outside the body of a function, the initializer list shall
3977 consist of constant expressions.
3978 <h6>Semantics</h6>
3979 <p><!--para 4 -->
3980 A postfix expression that consists of a parenthesized type name followed by a brace-
3981 enclosed list of initializers is a compound literal. It provides an unnamed object whose
3983 <p><!--para 5 -->
3984 If the type name specifies an array of unknown size, the size is determined by the
3985 initializer list as specified in <a href="#6.7.8">6.7.8</a>, and the type of the compound literal is that of the
3986 completed array type. Otherwise (when the type name specifies an object type), the type
3987 of the compound literal is that specified by the type name. In either case, the result is an
3988 lvalue.
3991 <!--page 88 -->
3992 <p><!--para 6 -->
3993 The value of the compound literal is that of an unnamed object initialized by the
3994 initializer list. If the compound literal occurs outside the body of a function, the object
3995 has static storage duration; otherwise, it has automatic storage duration associated with
3996 the enclosing block.
3997 <p><!--para 7 -->
3998 All the semantic rules and constraints for initializer lists in <a href="#6.7.8">6.7.8</a> are applicable to
4000 <p><!--para 8 -->
4001 String literals, and compound literals with const-qualified types, need not designate
4003 <p><!--para 9 -->
4004 EXAMPLE 1 The file scope definition
4005 <pre>
4006 int *p = (int []){2, 4};</pre>
4007 initializes p to point to the first element of an array of two ints, the first having the value two and the
4008 second, four. The expressions in this compound literal are required to be constant. The unnamed object
4009 has static storage duration.
4011 <p><!--para 10 -->
4012 EXAMPLE 2 In contrast, in
4013 <pre>
4014 void f(void)
4015 {
4016 int *p;
4017 /*...*/
4018 p = (int [2]){*p};
4019 /*...*/
4020 }</pre>
4021 p is assigned the address of the first element of an array of two ints, the first having the value previously
4022 pointed to by p and the second, zero. The expressions in this compound literal need not be constant. The
4023 unnamed object has automatic storage duration.
4025 <p><!--para 11 -->
4026 EXAMPLE 3 Initializers with designations can be combined with compound literals. Structure objects
4027 created using compound literals can be passed to functions without depending on member order:
4028 <pre>
4029 drawline((struct point){.x=1, .y=1},
4030 (struct point){.x=3, .y=4});</pre>
4031 Or, if drawline instead expected pointers to struct point:
4032 <pre>
4033 drawline(&(struct point){.x=1, .y=1},
4034 &(struct point){.x=3, .y=4});</pre>
4036 <p><!--para 12 -->
4037 EXAMPLE 4 A read-only compound literal can be specified through constructions like:
4038 <pre>
4039 (const float []){1e0, 1e1, 1e2, 1e3, 1e4, 1e5, 1e6}</pre>
4044 <!--page 89 -->
4045 <p><!--para 13 -->
4046 EXAMPLE 5 The following three expressions have different meanings:
4047 <pre>
4051 The first always has static storage duration and has type array of char, but need not be modifiable; the last
4052 two have automatic storage duration when they occur within the body of a function, and the first of these
4053 two is modifiable.
4055 <p><!--para 14 -->
4056 EXAMPLE 6 Like string literals, const-qualified compound literals can be placed into read-only memory
4057 and can even be shared. For example,
4058 <pre>
4060 might yield 1 if the literals' storage is shared.
4062 <p><!--para 15 -->
4063 EXAMPLE 7 Since compound literals are unnamed, a single compound literal cannot specify a circularly
4064 linked object. For example, there is no way to write a self-referential compound literal that could be used
4065 as the function argument in place of the named object endless_zeros below:
4066 <pre>
4067 struct int_list { int car; struct int_list *cdr; };
4068 struct int_list endless_zeros = {0, &endless_zeros};
4069 eval(endless_zeros);</pre>
4071 <p><!--para 16 -->
4072 EXAMPLE 8 Each compound literal creates only a single object in a given scope:
4073 <pre>
4074 struct s { int i; };
4075 int f (void)
4076 {
4077 struct s *p = 0, *q;
4078 int j = 0;
4079 again:
4080 q = p, p = &((struct s){ j++ });
4081 if (j < 2) goto again;
4082 return p == q && q->i == 1;
4083 }</pre>
4084 The function f() always returns the value 1.
4085 <p><!--para 17 -->
4086 Note that if an iteration statement were used instead of an explicit goto and a labeled statement, the
4087 lifetime of the unnamed object would be the body of the loop only, and on entry next time around p would
4088 have an indeterminate value, which would result in undefined behavior.
4090 <p><b> Forward references</b>: type names (<a href="#6.7.6">6.7.6</a>), initialization (<a href="#6.7.8">6.7.8</a>).
4091 <!--page 90 -->
4093 <h6>footnotes</h6>
4094 <p><small><a name="note84" href="#note84">84)</a> Note that this differs from a cast expression. For example, a cast specifies a conversion to scalar types
4095 or void only, and the result of a cast expression is not an lvalue.
4096 </small>
4097 <p><small><a name="note85" href="#note85">85)</a> For example, subobjects without explicit initializers are initialized to zero.
4098 </small>
4099 <p><small><a name="note86" href="#note86">86)</a> This allows implementations to share storage for string literals and constant compound literals with
4100 the same or overlapping representations.
4101 </small>
4104 <h6>Syntax</h6>
4105 <p><!--para 1 -->
4106 <pre>
4107 unary-expression:
4108 postfix-expression
4109 ++ unary-expression
4110 -- unary-expression
4111 unary-operator cast-expression
4112 sizeof unary-expression
4113 sizeof ( type-name )
4114 unary-operator: one of
4115 & * + - ~ !</pre>
4117 <h5><a name="6.5.3.1" href="#6.5.3.1">6.5.3.1 Prefix increment and decrement operators</a></h5>
4118 <h6>Constraints</h6>
4119 <p><!--para 1 -->
4120 The operand of the prefix increment or decrement operator shall have qualified or
4121 unqualified real or pointer type and shall be a modifiable lvalue.
4122 <h6>Semantics</h6>
4123 <p><!--para 2 -->
4124 The value of the operand of the prefix ++ operator is incremented. The result is the new
4125 value of the operand after incrementation. The expression ++E is equivalent to (E+=1).
4126 See the discussions of additive operators and compound assignment for information on
4127 constraints, types, side effects, and conversions and the effects of operations on pointers.
4128 <p><!--para 3 -->
4129 The prefix -- operator is analogous to the prefix ++ operator, except that the value of the
4130 operand is decremented.
4131 <p><b> Forward references</b>: additive operators (<a href="#6.5.6">6.5.6</a>), compound assignment (<a href="#6.5.16.2">6.5.16.2</a>).
4134 <h6>Constraints</h6>
4135 <p><!--para 1 -->
4136 The operand of the unary & operator shall be either a function designator, the result of a
4137 [] or unary * operator, or an lvalue that designates an object that is not a bit-field and is
4138 not declared with the register storage-class specifier.
4139 <p><!--para 2 -->
4140 The operand of the unary * operator shall have pointer type.
4141 <h6>Semantics</h6>
4142 <p><!--para 3 -->
4143 The unary & operator yields the address of its operand. If the operand has type ''type'',
4144 the result has type ''pointer to type''. If the operand is the result of a unary * operator,
4145 neither that operator nor the & operator is evaluated and the result is as if both were
4146 omitted, except that the constraints on the operators still apply and the result is not an
4147 lvalue. Similarly, if the operand is the result of a [] operator, neither the & operator nor
4148 <!--page 91 -->
4149 the unary * that is implied by the [] is evaluated and the result is as if the & operator
4150 were removed and the [] operator were changed to a + operator. Otherwise, the result is
4151 a pointer to the object or function designated by its operand.
4152 <p><!--para 4 -->
4153 The unary * operator denotes indirection. If the operand points to a function, the result is
4154 a function designator; if it points to an object, the result is an lvalue designating the
4155 object. If the operand has type ''pointer to type'', the result has type ''type''. If an
4156 invalid value has been assigned to the pointer, the behavior of the unary * operator is
4158 <p><b> Forward references</b>: storage-class specifiers (<a href="#6.7.1">6.7.1</a>), structure and union specifiers
4161 <h6>footnotes</h6>
4162 <p><small><a name="note87" href="#note87">87)</a> Thus, &*E is equivalent to E (even if E is a null pointer), and &(E1[E2]) to ((E1)+(E2)). It is
4163 always true that if E is a function designator or an lvalue that is a valid operand of the unary &
4164 operator, *&E is a function designator or an lvalue equal to E. If *P is an lvalue and T is the name of
4165 an object pointer type, *(T)P is an lvalue that has a type compatible with that to which T points.
4166 Among the invalid values for dereferencing a pointer by the unary * operator are a null pointer, an
4167 address inappropriately aligned for the type of object pointed to, and the address of an object after the
4168 end of its lifetime.
4169 </small>
4172 <h6>Constraints</h6>
4173 <p><!--para 1 -->
4174 The operand of the unary + or - operator shall have arithmetic type; of the ~ operator,
4175 integer type; of the ! operator, scalar type.
4176 <h6>Semantics</h6>
4177 <p><!--para 2 -->
4178 The result of the unary + operator is the value of its (promoted) operand. The integer
4179 promotions are performed on the operand, and the result has the promoted type.
4180 <p><!--para 3 -->
4181 The result of the unary - operator is the negative of its (promoted) operand. The integer
4182 promotions are performed on the operand, and the result has the promoted type.
4183 <p><!--para 4 -->
4184 The result of the ~ operator is the bitwise complement of its (promoted) operand (that is,
4185 each bit in the result is set if and only if the corresponding bit in the converted operand is
4186 not set). The integer promotions are performed on the operand, and the result has the
4187 promoted type. If the promoted type is an unsigned type, the expression ~E is equivalent
4188 to the maximum value representable in that type minus E.
4189 <p><!--para 5 -->
4190 The result of the logical negation operator ! is 0 if the value of its operand compares
4191 unequal to 0, 1 if the value of its operand compares equal to 0. The result has type int.
4192 The expression !E is equivalent to (0==E).
4197 <!--page 92 -->
4200 <h6>Constraints</h6>
4201 <p><!--para 1 -->
4202 The sizeof operator shall not be applied to an expression that has function type or an
4203 incomplete type, to the parenthesized name of such a type, or to an expression that
4204 designates a bit-field member.
4205 <h6>Semantics</h6>
4206 <p><!--para 2 -->
4207 The sizeof operator yields the size (in bytes) of its operand, which may be an
4208 expression or the parenthesized name of a type. The size is determined from the type of
4209 the operand. The result is an integer. If the type of the operand is a variable length array
4210 type, the operand is evaluated; otherwise, the operand is not evaluated and the result is an
4211 integer constant.
4212 <p><!--para 3 -->
4213 When applied to an operand that has type char, unsigned char, or signed char,
4214 (or a qualified version thereof) the result is 1. When applied to an operand that has array
4215 type, the result is the total number of bytes in the array.<sup><a href="#note88"><b>88)</b></a></sup> When applied to an operand
4216 that has structure or union type, the result is the total number of bytes in such an object,
4217 including internal and trailing padding.
4218 <p><!--para 4 -->
4219 The value of the result is implementation-defined, and its type (an unsigned integer type)
4221 <p><!--para 5 -->
4222 EXAMPLE 1 A principal use of the sizeof operator is in communication with routines such as storage
4223 allocators and I/O systems. A storage-allocation function might accept a size (in bytes) of an object to
4224 allocate and return a pointer to void. For example:
4225 <pre>
4226 extern void *alloc(size_t);
4227 double *dp = alloc(sizeof *dp);</pre>
4228 The implementation of the alloc function should ensure that its return value is aligned suitably for
4229 conversion to a pointer to double.
4231 <p><!--para 6 -->
4232 EXAMPLE 2 Another use of the sizeof operator is to compute the number of elements in an array:
4233 <pre>
4234 sizeof array / sizeof array[0]</pre>
4236 <p><!--para 7 -->
4237 EXAMPLE 3 In this example, the size of a variable length array is computed and returned from a
4238 function:
4239 <pre>
4241 size_t fsize3(int n)
4242 {
4243 char b[n+3]; // variable length array
4244 return sizeof b; // execution time sizeof
4245 }</pre>
4249 <!--page 93 -->
4250 <pre>
4251 int main()
4252 {
4253 size_t size;
4254 size = fsize3(10); // fsize3 returns 13
4255 return 0;
4256 }</pre>
4258 <p><b> Forward references</b>: common definitions <a href="#7.17"><stddef.h></a> (<a href="#7.17">7.17</a>), declarations (<a href="#6.7">6.7</a>),
4259 structure and union specifiers (<a href="#6.7.2.1">6.7.2.1</a>), type names (<a href="#6.7.6">6.7.6</a>), array declarators (<a href="#6.7.5.2">6.7.5.2</a>).
4261 <h6>footnotes</h6>
4262 <p><small><a name="note88" href="#note88">88)</a> When applied to a parameter declared to have array or function type, the sizeof operator yields the
4264 </small>
4267 <h6>Syntax</h6>
4268 <p><!--para 1 -->
4269 <pre>
4270 cast-expression:
4271 unary-expression
4272 ( type-name ) cast-expression</pre>
4273 <h6>Constraints</h6>
4274 <p><!--para 2 -->
4275 Unless the type name specifies a void type, the type name shall specify qualified or
4276 unqualified scalar type and the operand shall have scalar type.
4277 <p><!--para 3 -->
4278 Conversions that involve pointers, other than where permitted by the constraints of
4280 <h6>Semantics</h6>
4281 <p><!--para 4 -->
4282 Preceding an expression by a parenthesized type name converts the value of the
4283 expression to the named type. This construction is called a cast.<sup><a href="#note89"><b>89)</b></a></sup> A cast that specifies
4284 no conversion has no effect on the type or value of an expression.
4285 <p><!--para 5 -->
4286 If the value of the expression is represented with greater precision or range than required
4287 by the type named by the cast (<a href="#6.3.1.8">6.3.1.8</a>), then the cast specifies a conversion even if the
4288 type of the expression is the same as the named type.
4289 <p><b> Forward references</b>: equality operators (<a href="#6.5.9">6.5.9</a>), function declarators (including
4290 prototypes) (<a href="#6.7.5.3">6.7.5.3</a>), simple assignment (<a href="#6.5.16.1">6.5.16.1</a>), type names (<a href="#6.7.6">6.7.6</a>).
4295 <!--page 94 -->
4297 <h6>footnotes</h6>
4298 <p><small><a name="note89" href="#note89">89)</a> A cast does not yield an lvalue. Thus, a cast to a qualified type has the same effect as a cast to the
4299 unqualified version of the type.
4300 </small>
4303 <h6>Syntax</h6>
4304 <p><!--para 1 -->
4305 <pre>
4306 multiplicative-expression:
4307 cast-expression
4308 multiplicative-expression * cast-expression
4309 multiplicative-expression / cast-expression
4310 multiplicative-expression % cast-expression</pre>
4311 <h6>Constraints</h6>
4312 <p><!--para 2 -->
4313 Each of the operands shall have arithmetic type. The operands of the % operator shall
4314 have integer type.
4315 <h6>Semantics</h6>
4316 <p><!--para 3 -->
4317 The usual arithmetic conversions are performed on the operands.
4318 <p><!--para 4 -->
4319 The result of the binary * operator is the product of the operands.
4320 <p><!--para 5 -->
4321 The result of the / operator is the quotient from the division of the first operand by the
4322 second; the result of the % operator is the remainder. In both operations, if the value of
4323 the second operand is zero, the behavior is undefined.
4324 <p><!--para 6 -->
4325 When integers are divided, the result of the / operator is the algebraic quotient with any
4326 fractional part discarded.<sup><a href="#note90"><b>90)</b></a></sup> If the quotient a/b is representable, the expression
4327 (a/b)*b + a%b shall equal a.
4329 <h6>footnotes</h6>
4330 <p><small><a name="note90" href="#note90">90)</a> This is often called ''truncation toward zero''.
4331 </small>
4334 <h6>Syntax</h6>
4335 <p><!--para 1 -->
4336 <pre>
4337 additive-expression:
4338 multiplicative-expression
4339 additive-expression + multiplicative-expression
4340 additive-expression - multiplicative-expression</pre>
4341 <h6>Constraints</h6>
4342 <p><!--para 2 -->
4343 For addition, either both operands shall have arithmetic type, or one operand shall be a
4344 pointer to an object type and the other shall have integer type. (Incrementing is
4345 equivalent to adding 1.)
4346 <p><!--para 3 -->
4347 For subtraction, one of the following shall hold:
4348 <ul>
4349 <li> both operands have arithmetic type;
4353 <!--page 95 -->
4354 <li> both operands are pointers to qualified or unqualified versions of compatible object
4355 types; or
4356 <li> the left operand is a pointer to an object type and the right operand has integer type.
4357 </ul>
4358 (Decrementing is equivalent to subtracting 1.)
4359 <h6>Semantics</h6>
4360 <p><!--para 4 -->
4361 If both operands have arithmetic type, the usual arithmetic conversions are performed on
4362 them.
4363 <p><!--para 5 -->
4364 The result of the binary + operator is the sum of the operands.
4365 <p><!--para 6 -->
4366 The result of the binary - operator is the difference resulting from the subtraction of the
4367 second operand from the first.
4368 <p><!--para 7 -->
4369 For the purposes of these operators, a pointer to an object that is not an element of an
4370 array behaves the same as a pointer to the first element of an array of length one with the
4371 type of the object as its element type.
4372 <p><!--para 8 -->
4373 When an expression that has integer type is added to or subtracted from a pointer, the
4374 result has the type of the pointer operand. If the pointer operand points to an element of
4375 an array object, and the array is large enough, the result points to an element offset from
4376 the original element such that the difference of the subscripts of the resulting and original
4377 array elements equals the integer expression. In other words, if the expression P points to
4378 the i-th element of an array object, the expressions (P)+N (equivalently, N+(P)) and
4379 (P)-N (where N has the value n) point to, respectively, the i+n-th and i-n-th elements of
4380 the array object, provided they exist. Moreover, if the expression P points to the last
4381 element of an array object, the expression (P)+1 points one past the last element of the
4382 array object, and if the expression Q points one past the last element of an array object,
4383 the expression (Q)-1 points to the last element of the array object. If both the pointer
4384 operand and the result point to elements of the same array object, or one past the last
4385 element of the array object, the evaluation shall not produce an overflow; otherwise, the
4386 behavior is undefined. If the result points one past the last element of the array object, it
4387 shall not be used as the operand of a unary * operator that is evaluated.
4388 <p><!--para 9 -->
4389 When two pointers are subtracted, both shall point to elements of the same array object,
4390 or one past the last element of the array object; the result is the difference of the
4391 subscripts of the two array elements. The size of the result is implementation-defined,
4392 and its type (a signed integer type) is ptrdiff_t defined in the <a href="#7.17"><stddef.h></a> header.
4393 If the result is not representable in an object of that type, the behavior is undefined. In
4394 other words, if the expressions P and Q point to, respectively, the i-th and j-th elements of
4395 an array object, the expression (P)-(Q) has the value i-j provided the value fits in an
4396 object of type ptrdiff_t. Moreover, if the expression P points either to an element of
4397 an array object or one past the last element of an array object, and the expression Q points
4398 to the last element of the same array object, the expression ((Q)+1)-(P) has the same
4399 <!--page 96 -->
4400 value as ((Q)-(P))+1 and as -((P)-((Q)+1)), and has the value zero if the
4401 expression P points one past the last element of the array object, even though the
4402 expression (Q)+1 does not point to an element of the array object.<sup><a href="#note91"><b>91)</b></a></sup>
4403 <p><!--para 10 -->
4404 EXAMPLE Pointer arithmetic is well defined with pointers to variable length array types.
4405 <p><!--para 11 -->
4406 <pre>
4407 {
4408 int n = 4, m = 3;
4409 int a[n][m];
4410 int (*p)[m] = a; // p == &a[0]
4411 p += 1; // p == &a[1]
4412 (*p)[2] = 99; // a[1][2] == 99
4413 n = p - a; // n == 1
4414 }</pre>
4415 If array a in the above example were declared to be an array of known constant size, and pointer p were
4416 declared to be a pointer to an array of the same known constant size (pointing to a), the results would be
4417 the same.
4419 <p><b> Forward references</b>: array declarators (<a href="#6.7.5.2">6.7.5.2</a>), common definitions <a href="#7.17"><stddef.h></a>
4422 <h6>footnotes</h6>
4423 <p><small><a name="note91" href="#note91">91)</a> Another way to approach pointer arithmetic is first to convert the pointer(s) to character pointer(s): In
4424 this scheme the integer expression added to or subtracted from the converted pointer is first multiplied
4425 by the size of the object originally pointed to, and the resulting pointer is converted back to the
4426 original type. For pointer subtraction, the result of the difference between the character pointers is
4427 similarly divided by the size of the object originally pointed to.
4428 When viewed in this way, an implementation need only provide one extra byte (which may overlap
4429 another object in the program) just after the end of the object in order to satisfy the ''one past the last
4430 element'' requirements.
4431 </small>
4434 <h6>Syntax</h6>
4435 <p><!--para 1 -->
4436 <pre>
4437 shift-expression:
4438 additive-expression
4439 shift-expression << additive-expression
4440 shift-expression >> additive-expression</pre>
4441 <h6>Constraints</h6>
4442 <p><!--para 2 -->
4443 Each of the operands shall have integer type.
4444 <h6>Semantics</h6>
4445 <p><!--para 3 -->
4446 The integer promotions are performed on each of the operands. The type of the result is
4447 that of the promoted left operand. If the value of the right operand is negative or is
4448 greater than or equal to the width of the promoted left operand, the behavior is undefined.
4453 <!--page 97 -->
4454 <p><!--para 4 -->
4455 The result of E1 << E2 is E1 left-shifted E2 bit positions; vacated bits are filled with
4456 zeros. If E1 has an unsigned type, the value of the result is E1 x 2E2 , reduced modulo
4457 one more than the maximum value representable in the result type. If E1 has a signed
4458 type and nonnegative value, and E1 x 2E2 is representable in the result type, then that is
4459 the resulting value; otherwise, the behavior is undefined.
4460 <p><!--para 5 -->
4461 The result of E1 >> E2 is E1 right-shifted E2 bit positions. If E1 has an unsigned type
4462 or if E1 has a signed type and a nonnegative value, the value of the result is the integral
4463 part of the quotient of E1 / 2E2 . If E1 has a signed type and a negative value, the
4464 resulting value is implementation-defined.
4467 <h6>Syntax</h6>
4468 <p><!--para 1 -->
4469 <pre>
4470 relational-expression:
4471 shift-expression
4472 relational-expression < shift-expression
4473 relational-expression > shift-expression
4474 relational-expression <= shift-expression
4475 relational-expression >= shift-expression</pre>
4476 <h6>Constraints</h6>
4477 <p><!--para 2 -->
4478 One of the following shall hold:
4479 <ul>
4480 <li> both operands have real type;
4481 <li> both operands are pointers to qualified or unqualified versions of compatible object
4482 types; or
4483 <li> both operands are pointers to qualified or unqualified versions of compatible
4484 incomplete types.
4485 </ul>
4486 <h6>Semantics</h6>
4487 <p><!--para 3 -->
4488 If both of the operands have arithmetic type, the usual arithmetic conversions are
4489 performed.
4490 <p><!--para 4 -->
4491 For the purposes of these operators, a pointer to an object that is not an element of an
4492 array behaves the same as a pointer to the first element of an array of length one with the
4493 type of the object as its element type.
4494 <p><!--para 5 -->
4495 When two pointers are compared, the result depends on the relative locations in the
4496 address space of the objects pointed to. If two pointers to object or incomplete types both
4497 point to the same object, or both point one past the last element of the same array object,
4498 they compare equal. If the objects pointed to are members of the same aggregate object,
4499 pointers to structure members declared later compare greater than pointers to members
4500 declared earlier in the structure, and pointers to array elements with larger subscript
4501 <!--page 98 -->
4502 values compare greater than pointers to elements of the same array with lower subscript
4503 values. All pointers to members of the same union object compare equal. If the
4504 expression P points to an element of an array object and the expression Q points to the
4505 last element of the same array object, the pointer expression Q+1 compares greater than
4506 P. In all other cases, the behavior is undefined.
4507 <p><!--para 6 -->
4508 Each of the operators < (less than), > (greater than), <= (less than or equal to), and >=
4509 (greater than or equal to) shall yield 1 if the specified relation is true and 0 if it is false.<sup><a href="#note92"><b>92)</b></a></sup>
4510 The result has type int.
4512 <h6>footnotes</h6>
4513 <p><small><a name="note92" href="#note92">92)</a> The expression a<b<c is not interpreted as in ordinary mathematics. As the syntax indicates, it
4514 means (a<b)<c; in other words, ''if a is less than b, compare 1 to c; otherwise, compare 0 to c''.
4515 </small>
4518 <h6>Syntax</h6>
4519 <p><!--para 1 -->
4520 <pre>
4521 equality-expression:
4522 relational-expression
4523 equality-expression == relational-expression
4524 equality-expression != relational-expression</pre>
4525 <h6>Constraints</h6>
4526 <p><!--para 2 -->
4527 One of the following shall hold:
4528 <ul>
4529 <li> both operands have arithmetic type;
4530 <li> both operands are pointers to qualified or unqualified versions of compatible types;
4531 <li> one operand is a pointer to an object or incomplete type and the other is a pointer to a
4532 qualified or unqualified version of void; or
4533 <li> one operand is a pointer and the other is a null pointer constant.
4534 </ul>
4535 <h6>Semantics</h6>
4536 <p><!--para 3 -->
4537 The == (equal to) and != (not equal to) operators are analogous to the relational
4538 operators except for their lower precedence.<sup><a href="#note93"><b>93)</b></a></sup> Each of the operators yields 1 if the
4539 specified relation is true and 0 if it is false. The result has type int. For any pair of
4540 operands, exactly one of the relations is true.
4541 <p><!--para 4 -->
4542 If both of the operands have arithmetic type, the usual arithmetic conversions are
4543 performed. Values of complex types are equal if and only if both their real parts are equal
4544 and also their imaginary parts are equal. Any two values of arithmetic types from
4545 different type domains are equal if and only if the results of their conversions to the
4546 (complex) result type determined by the usual arithmetic conversions are equal.
4549 <!--page 99 -->
4550 <p><!--para 5 -->
4551 Otherwise, at least one operand is a pointer. If one operand is a pointer and the other is a
4552 null pointer constant, the null pointer constant is converted to the type of the pointer. If
4553 one operand is a pointer to an object or incomplete type and the other is a pointer to a
4554 qualified or unqualified version of void, the former is converted to the type of the latter.
4555 <p><!--para 6 -->
4556 Two pointers compare equal if and only if both are null pointers, both are pointers to the
4557 same object (including a pointer to an object and a subobject at its beginning) or function,
4558 both are pointers to one past the last element of the same array object, or one is a pointer
4559 to one past the end of one array object and the other is a pointer to the start of a different
4560 array object that happens to immediately follow the first array object in the address
4562 <p><!--para 7 -->
4563 For the purposes of these operators, a pointer to an object that is not an element of an
4564 array behaves the same as a pointer to the first element of an array of length one with the
4565 type of the object as its element type.
4567 <h6>footnotes</h6>
4568 <p><small><a name="note93" href="#note93">93)</a> Because of the precedences, a<b == c<d is 1 whenever a<b and c<d have the same truth-value.
4569 </small>
4570 <p><small><a name="note94" href="#note94">94)</a> Two objects may be adjacent in memory because they are adjacent elements of a larger array or
4571 adjacent members of a structure with no padding between them, or because the implementation chose
4572 to place them so, even though they are unrelated. If prior invalid pointer operations (such as accesses
4573 outside array bounds) produced undefined behavior, subsequent comparisons also produce undefined
4574 behavior.
4575 </small>
4578 <h6>Syntax</h6>
4579 <p><!--para 1 -->
4580 <pre>
4581 AND-expression:
4582 equality-expression
4583 AND-expression & equality-expression</pre>
4584 <h6>Constraints</h6>
4585 <p><!--para 2 -->
4586 Each of the operands shall have integer type.
4587 <h6>Semantics</h6>
4588 <p><!--para 3 -->
4589 The usual arithmetic conversions are performed on the operands.
4590 <p><!--para 4 -->
4591 The result of the binary & operator is the bitwise AND of the operands (that is, each bit in
4592 the result is set if and only if each of the corresponding bits in the converted operands is
4593 set).
4598 <!--page 100 -->
4601 <h6>Syntax</h6>
4602 <p><!--para 1 -->
4603 <pre>
4604 exclusive-OR-expression:
4605 AND-expression
4606 exclusive-OR-expression ^ AND-expression</pre>
4607 <h6>Constraints</h6>
4608 <p><!--para 2 -->
4609 Each of the operands shall have integer type.
4610 <h6>Semantics</h6>
4611 <p><!--para 3 -->
4612 The usual arithmetic conversions are performed on the operands.
4613 <p><!--para 4 -->
4614 The result of the ^ operator is the bitwise exclusive OR of the operands (that is, each bit
4615 in the result is set if and only if exactly one of the corresponding bits in the converted
4616 operands is set).
4619 <h6>Syntax</h6>
4620 <p><!--para 1 -->
4621 <pre>
4622 inclusive-OR-expression:
4623 exclusive-OR-expression
4624 inclusive-OR-expression | exclusive-OR-expression</pre>
4625 <h6>Constraints</h6>
4626 <p><!--para 2 -->
4627 Each of the operands shall have integer type.
4628 <h6>Semantics</h6>
4629 <p><!--para 3 -->
4630 The usual arithmetic conversions are performed on the operands.
4631 <p><!--para 4 -->
4632 The result of the | operator is the bitwise inclusive OR of the operands (that is, each bit in
4633 the result is set if and only if at least one of the corresponding bits in the converted
4634 operands is set).
4635 <!--page 101 -->
4638 <h6>Syntax</h6>
4639 <p><!--para 1 -->
4640 <pre>
4641 logical-AND-expression:
4642 inclusive-OR-expression
4643 logical-AND-expression && inclusive-OR-expression</pre>
4644 <h6>Constraints</h6>
4645 <p><!--para 2 -->
4646 Each of the operands shall have scalar type.
4647 <h6>Semantics</h6>
4648 <p><!--para 3 -->
4649 The && operator shall yield 1 if both of its operands compare unequal to 0; otherwise, it
4650 yields 0. The result has type int.
4651 <p><!--para 4 -->
4652 Unlike the bitwise binary & operator, the && operator guarantees left-to-right evaluation;
4653 there is a sequence point after the evaluation of the first operand. If the first operand
4654 compares equal to 0, the second operand is not evaluated.
4657 <h6>Syntax</h6>
4658 <p><!--para 1 -->
4659 <pre>
4660 logical-OR-expression:
4661 logical-AND-expression
4662 logical-OR-expression || logical-AND-expression</pre>
4663 <h6>Constraints</h6>
4664 <p><!--para 2 -->
4665 Each of the operands shall have scalar type.
4666 <h6>Semantics</h6>
4667 <p><!--para 3 -->
4668 The || operator shall yield 1 if either of its operands compare unequal to 0; otherwise, it
4669 yields 0. The result has type int.
4670 <p><!--para 4 -->
4671 Unlike the bitwise | operator, the || operator guarantees left-to-right evaluation; there is
4672 a sequence point after the evaluation of the first operand. If the first operand compares
4673 unequal to 0, the second operand is not evaluated.
4674 <!--page 102 -->
4677 <h6>Syntax</h6>
4678 <p><!--para 1 -->
4679 <pre>
4680 conditional-expression:
4681 logical-OR-expression
4682 logical-OR-expression ? expression : conditional-expression</pre>
4683 <h6>Constraints</h6>
4684 <p><!--para 2 -->
4685 The first operand shall have scalar type.
4686 <p><!--para 3 -->
4687 One of the following shall hold for the second and third operands:
4688 <ul>
4689 <li> both operands have arithmetic type;
4690 <li> both operands have the same structure or union type;
4691 <li> both operands have void type;
4692 <li> both operands are pointers to qualified or unqualified versions of compatible types;
4693 <li> one operand is a pointer and the other is a null pointer constant; or
4694 <li> one operand is a pointer to an object or incomplete type and the other is a pointer to a
4695 qualified or unqualified version of void.
4696 </ul>
4697 <h6>Semantics</h6>
4698 <p><!--para 4 -->
4699 The first operand is evaluated; there is a sequence point after its evaluation. The second
4700 operand is evaluated only if the first compares unequal to 0; the third operand is evaluated
4701 only if the first compares equal to 0; the result is the value of the second or third operand
4702 (whichever is evaluated), converted to the type described below.<sup><a href="#note95"><b>95)</b></a></sup> If an attempt is made
4703 to modify the result of a conditional operator or to access it after the next sequence point,
4704 the behavior is undefined.
4705 <p><!--para 5 -->
4706 If both the second and third operands have arithmetic type, the result type that would be
4707 determined by the usual arithmetic conversions, were they applied to those two operands,
4708 is the type of the result. If both the operands have structure or union type, the result has
4709 that type. If both operands have void type, the result has void type.
4710 <p><!--para 6 -->
4711 If both the second and third operands are pointers or one is a null pointer constant and the
4712 other is a pointer, the result type is a pointer to a type qualified with all the type qualifiers
4713 of the types pointed-to by both operands. Furthermore, if both operands are pointers to
4714 compatible types or to differently qualified versions of compatible types, the result type is
4715 a pointer to an appropriately qualified version of the composite type; if one operand is a
4716 null pointer constant, the result has the type of the other operand; otherwise, one operand
4717 is a pointer to void or a qualified version of void, in which case the result type is a
4719 <!--page 103 -->
4720 pointer to an appropriately qualified version of void.
4721 <p><!--para 7 -->
4722 EXAMPLE The common type that results when the second and third operands are pointers is determined
4723 in two independent stages. The appropriate qualifiers, for example, do not depend on whether the two
4724 pointers have compatible types.
4725 <p><!--para 8 -->
4726 Given the declarations
4727 <pre>
4728 const void *c_vp;
4729 void *vp;
4730 const int *c_ip;
4731 volatile int *v_ip;
4732 int *ip;
4733 const char *c_cp;</pre>
4734 the third column in the following table is the common type that is the result of a conditional expression in
4735 which the first two columns are the second and third operands (in either order):
4736 <pre>
4737 c_vp c_ip const void *
4738 v_ip 0 volatile int *
4739 c_ip v_ip const volatile int *
4740 vp c_cp const void *
4741 ip c_ip const int *
4742 vp ip void *</pre>
4745 <h6>footnotes</h6>
4746 <p><small><a name="note95" href="#note95">95)</a> A conditional expression does not yield an lvalue.
4747 </small>
4750 <h6>Syntax</h6>
4751 <p><!--para 1 -->
4752 <pre>
4753 assignment-expression:
4754 conditional-expression
4755 unary-expression assignment-operator assignment-expression
4756 assignment-operator: one of
4757 = *= /= %= += -= <<= >>= &= ^= |=</pre>
4758 <h6>Constraints</h6>
4759 <p><!--para 2 -->
4760 An assignment operator shall have a modifiable lvalue as its left operand.
4761 <h6>Semantics</h6>
4762 <p><!--para 3 -->
4763 An assignment operator stores a value in the object designated by the left operand. An
4764 assignment expression has the value of the left operand after the assignment, but is not an
4765 lvalue. The type of an assignment expression is the type of the left operand unless the
4766 left operand has qualified type, in which case it is the unqualified version of the type of
4767 the left operand. The side effect of updating the stored value of the left operand shall
4768 occur between the previous and the next sequence point.
4769 <p><!--para 4 -->
4770 The order of evaluation of the operands is unspecified. If an attempt is made to modify
4771 the result of an assignment operator or to access it after the next sequence point, the
4772 behavior is undefined.
4773 <!--page 104 -->
4776 <h6>Constraints</h6>
4777 <p><!--para 1 -->
4779 <ul>
4780 <li> the left operand has qualified or unqualified arithmetic type and the right has
4781 arithmetic type;
4782 <li> the left operand has a qualified or unqualified version of a structure or union type
4783 compatible with the type of the right;
4784 <li> both operands are pointers to qualified or unqualified versions of compatible types,
4785 and the type pointed to by the left has all the qualifiers of the type pointed to by the
4786 right;
4787 <li> one operand is a pointer to an object or incomplete type and the other is a pointer to a
4788 qualified or unqualified version of void, and the type pointed to by the left has all
4789 the qualifiers of the type pointed to by the right;
4790 <li> the left operand is a pointer and the right is a null pointer constant; or
4791 <li> the left operand has type _Bool and the right is a pointer.
4792 </ul>
4793 <h6>Semantics</h6>
4794 <p><!--para 2 -->
4795 In simple assignment (=), the value of the right operand is converted to the type of the
4796 assignment expression and replaces the value stored in the object designated by the left
4797 operand.
4798 <p><!--para 3 -->
4799 If the value being stored in an object is read from another object that overlaps in any way
4800 the storage of the first object, then the overlap shall be exact and the two objects shall
4801 have qualified or unqualified versions of a compatible type; otherwise, the behavior is
4802 undefined.
4803 <p><!--para 4 -->
4804 EXAMPLE 1 In the program fragment
4805 <pre>
4806 int f(void);
4807 char c;
4808 /* ... */
4809 if ((c = f()) == -1)
4810 /* ... */</pre>
4811 the int value returned by the function may be truncated when stored in the char, and then converted back
4812 to int width prior to the comparison. In an implementation in which ''plain'' char has the same range of
4813 values as unsigned char (and char is narrower than int), the result of the conversion cannot be
4817 <!--page 105 -->
4818 negative, so the operands of the comparison can never compare equal. Therefore, for full portability, the
4819 variable c should be declared as int.
4821 <p><!--para 5 -->
4822 EXAMPLE 2 In the fragment:
4823 <pre>
4824 char c;
4825 int i;
4826 long l;
4827 l = (c = i);</pre>
4828 the value of i is converted to the type of the assignment expression c = i, that is, char type. The value
4829 of the expression enclosed in parentheses is then converted to the type of the outer assignment expression,
4830 that is, long int type.
4832 <p><!--para 6 -->
4833 EXAMPLE 3 Consider the fragment:
4834 <pre>
4835 const char **cpp;
4836 char *p;
4837 const char c = 'A';
4838 cpp = &p; // constraint violation
4839 *cpp = &c; // valid
4840 *p = 0; // valid</pre>
4841 The first assignment is unsafe because it would allow the following valid code to attempt to change the
4842 value of the const object c.
4845 <h6>footnotes</h6>
4846 <p><small><a name="note96" href="#note96">96)</a> The asymmetric appearance of these constraints with respect to type qualifiers is due to the conversion
4847 (specified in <a href="#6.3.2.1">6.3.2.1</a>) that changes lvalues to ''the value of the expression'' and thus removes any type
4848 qualifiers that were applied to the type category of the expression (for example, it removes const but
4849 not volatile from the type int volatile * const).
4850 </small>
4853 <h6>Constraints</h6>
4854 <p><!--para 1 -->
4855 For the operators += and -= only, either the left operand shall be a pointer to an object
4856 type and the right shall have integer type, or the left operand shall have qualified or
4857 unqualified arithmetic type and the right shall have arithmetic type.
4858 <p><!--para 2 -->
4859 For the other operators, each operand shall have arithmetic type consistent with those
4860 allowed by the corresponding binary operator.
4861 <h6>Semantics</h6>
4862 <p><!--para 3 -->
4863 A compound assignment of the form E1 op = E2 differs from the simple assignment
4864 expression E1 = E1 op (E2) only in that the lvalue E1 is evaluated only once.
4865 <!--page 106 -->
4868 <h6>Syntax</h6>
4869 <p><!--para 1 -->
4870 <pre>
4871 expression:
4872 assignment-expression
4873 expression , assignment-expression</pre>
4874 <h6>Semantics</h6>
4875 <p><!--para 2 -->
4876 The left operand of a comma operator is evaluated as a void expression; there is a
4877 sequence point after its evaluation. Then the right operand is evaluated; the result has its
4878 type and value.<sup><a href="#note97"><b>97)</b></a></sup> If an attempt is made to modify the result of a comma operator or to
4879 access it after the next sequence point, the behavior is undefined.
4880 <p><!--para 3 -->
4881 EXAMPLE As indicated by the syntax, the comma operator (as described in this subclause) cannot
4882 appear in contexts where a comma is used to separate items in a list (such as arguments to functions or lists
4883 of initializers). On the other hand, it can be used within a parenthesized expression or within the second
4884 expression of a conditional operator in such contexts. In the function call
4885 <pre>
4886 f(a, (t=3, t+2), c)</pre>
4887 the function has three arguments, the second of which has the value 5.
4894 <!--page 107 -->
4896 <h6>footnotes</h6>
4898 </small>
4901 <h6>Syntax</h6>
4902 <p><!--para 1 -->
4903 <pre>
4904 constant-expression:
4905 conditional-expression</pre>
4906 <h6>Description</h6>
4907 <p><!--para 2 -->
4908 A constant expression can be evaluated during translation rather than runtime, and
4909 accordingly may be used in any place that a constant may be.
4910 <h6>Constraints</h6>
4911 <p><!--para 3 -->
4912 Constant expressions shall not contain assignment, increment, decrement, function-call,
4913 or comma operators, except when they are contained within a subexpression that is not
4915 <p><!--para 4 -->
4916 Each constant expression shall evaluate to a constant that is in the range of representable
4917 values for its type.
4918 <h6>Semantics</h6>
4919 <p><!--para 5 -->
4920 An expression that evaluates to a constant is required in several contexts. If a floating
4921 expression is evaluated in the translation environment, the arithmetic precision and range
4922 shall be at least as great as if the expression were being evaluated in the execution
4923 environment.
4924 <p><!--para 6 -->
4925 An integer constant expression<sup><a href="#note99"><b>99)</b></a></sup> shall have integer type and shall only have operands
4926 that are integer constants, enumeration constants, character constants, sizeof
4927 expressions whose results are integer constants, and floating constants that are the
4928 immediate operands of casts. Cast operators in an integer constant expression shall only
4929 convert arithmetic types to integer types, except as part of an operand to the sizeof
4930 operator.
4931 <p><!--para 7 -->
4932 More latitude is permitted for constant expressions in initializers. Such a constant
4933 expression shall be, or evaluate to, one of the following:
4934 <ul>
4935 <li> an arithmetic constant expression,
4936 <li> a null pointer constant,
4941 <!--page 108 -->
4942 <li> an address constant, or
4943 <li> an address constant for an object type plus or minus an integer constant expression.
4944 </ul>
4945 <p><!--para 8 -->
4946 An arithmetic constant expression shall have arithmetic type and shall only have
4947 operands that are integer constants, floating constants, enumeration constants, character
4948 constants, and sizeof expressions. Cast operators in an arithmetic constant expression
4949 shall only convert arithmetic types to arithmetic types, except as part of an operand to a
4950 sizeof operator whose result is an integer constant.
4951 <p><!--para 9 -->
4952 An address constant is a null pointer, a pointer to an lvalue designating an object of static
4953 storage duration, or a pointer to a function designator; it shall be created explicitly using
4954 the unary & operator or an integer constant cast to pointer type, or implicitly by the use of
4955 an expression of array or function type. The array-subscript [] and member-access .
4956 and -> operators, the address & and indirection * unary operators, and pointer casts may
4957 be used in the creation of an address constant, but the value of an object shall not be
4958 accessed by use of these operators.
4959 <p><!--para 10 -->
4960 An implementation may accept other forms of constant expressions.
4961 <p><!--para 11 -->
4962 The semantic rules for the evaluation of a constant expression are the same as for
4964 <p><b> Forward references</b>: array declarators (<a href="#6.7.5.2">6.7.5.2</a>), initialization (<a href="#6.7.8">6.7.8</a>).
4969 <!--page 109 -->
4971 <h6>footnotes</h6>
4972 <p><small><a name="note98" href="#note98">98)</a> The operand of a sizeof operator is usually not evaluated (<a href="#6.5.3.4">6.5.3.4</a>).
4973 </small>
4974 <p><small><a name="note99" href="#note99">99)</a> An integer constant expression is used to specify the size of a bit-field member of a structure, the
4975 value of an enumeration constant, the size of an array, or the value of a case constant. Further
4976 constraints that apply to the integer constant expressions used in conditional-inclusion preprocessing
4978 </small>
4981 <pre>
4982 static int i = 2 || 1 / 0;</pre>
4983 the expression is a valid integer constant expression with value one.
4984 </small>
4987 <h6>Syntax</h6>
4988 <p><!--para 1 -->
4989 <pre>
4990 declaration:
4991 declaration-specifiers init-declarator-listopt ;
4992 declaration-specifiers:
4993 storage-class-specifier declaration-specifiersopt
4994 type-specifier declaration-specifiersopt
4995 type-qualifier declaration-specifiersopt
4996 function-specifier declaration-specifiersopt
4997 init-declarator-list:
4998 init-declarator
4999 init-declarator-list , init-declarator
5000 init-declarator:
5001 declarator
5002 declarator = initializer</pre>
5003 <h6>Constraints</h6>
5004 <p><!--para 2 -->
5005 A declaration shall declare at least a declarator (other than the parameters of a function or
5006 the members of a structure or union), a tag, or the members of an enumeration.
5007 <p><!--para 3 -->
5008 If an identifier has no linkage, there shall be no more than one declaration of the identifier
5009 (in a declarator or type specifier) with the same scope and in the same name space, except
5011 <p><!--para 4 -->
5012 All declarations in the same scope that refer to the same object or function shall specify
5013 compatible types.
5014 <h6>Semantics</h6>
5015 <p><!--para 5 -->
5016 A declaration specifies the interpretation and attributes of a set of identifiers. A definition
5017 of an identifier is a declaration for that identifier that:
5018 <ul>
5019 <li> for an object, causes storage to be reserved for that object;
5021 <li> for an enumeration constant or typedef name, is the (only) declaration of the
5022 identifier.
5023 </ul>
5024 <p><!--para 6 -->
5025 The declaration specifiers consist of a sequence of specifiers that indicate the linkage,
5026 storage duration, and part of the type of the entities that the declarators denote. The init-
5027 declarator-list is a comma-separated sequence of declarators, each of which may have
5029 <!--page 110 -->
5030 additional type information, or an initializer, or both. The declarators contain the
5031 identifiers (if any) being declared.
5032 <p><!--para 7 -->
5033 If an identifier for an object is declared with no linkage, the type for the object shall be
5034 complete by the end of its declarator, or by the end of its init-declarator if it has an
5035 initializer; in the case of function parameters (including in prototypes), it is the adjusted
5037 <p><b> Forward references</b>: declarators (<a href="#6.7.5">6.7.5</a>), enumeration specifiers (<a href="#6.7.2.2">6.7.2.2</a>), initialization
5040 <h6>footnotes</h6>
5041 <p><small><a name="note101" href="#note101">101)</a> Function definitions have a different syntax, described in <a href="#6.9.1">6.9.1</a>.
5042 </small>
5045 <h6>Syntax</h6>
5046 <p><!--para 1 -->
5047 <pre>
5048 storage-class-specifier:
5049 typedef
5050 extern
5051 static
5052 auto
5053 register</pre>
5054 <h6>Constraints</h6>
5055 <p><!--para 2 -->
5056 At most, one storage-class specifier may be given in the declaration specifiers in a
5058 <h6>Semantics</h6>
5059 <p><!--para 3 -->
5060 The typedef specifier is called a ''storage-class specifier'' for syntactic convenience
5061 only; it is discussed in <a href="#6.7.7">6.7.7</a>. The meanings of the various linkages and storage durations
5063 <p><!--para 4 -->
5064 A declaration of an identifier for an object with storage-class specifier register
5065 suggests that access to the object be as fast as possible. The extent to which such
5066 suggestions are effective is implementation-defined.<sup><a href="#note103"><b>103)</b></a></sup>
5067 <p><!--para 5 -->
5068 The declaration of an identifier for a function that has block scope shall have no explicit
5069 storage-class specifier other than extern.
5073 <!--page 111 -->
5074 <p><!--para 6 -->
5075 If an aggregate or union object is declared with a storage-class specifier other than
5076 typedef, the properties resulting from the storage-class specifier, except with respect to
5077 linkage, also apply to the members of the object, and so on recursively for any aggregate
5078 or union member objects.
5081 <h6>footnotes</h6>
5082 <p><small><a name="note102" href="#note102">102)</a> See ''future language directions'' (<a href="#6.11.5">6.11.5</a>).
5083 </small>
5084 <p><small><a name="note103" href="#note103">103)</a> The implementation may treat any register declaration simply as an auto declaration. However,
5085 whether or not addressable storage is actually used, the address of any part of an object declared with
5086 storage-class specifier register cannot be computed, either explicitly (by use of the unary &
5087 operator as discussed in <a href="#6.5.3.2">6.5.3.2</a>) or implicitly (by converting an array name to a pointer as discussed in
5088 <a href="#6.3.2.1">6.3.2.1</a>). Thus, the only operator that can be applied to an array declared with storage-class specifier
5089 register is sizeof.
5090 </small>
5093 <h6>Syntax</h6>
5094 <p><!--para 1 -->
5095 <pre>
5096 type-specifier:
5097 void
5098 char
5099 short
5100 int
5101 long
5102 float
5103 double
5104 signed
5105 unsigned
5106 _Bool
5107 _Complex
5108 struct-or-union-specifier *
5109 enum-specifier
5110 typedef-name</pre>
5111 <h6>Constraints</h6>
5112 <p><!--para 2 -->
5113 At least one type specifier shall be given in the declaration specifiers in each declaration,
5114 and in the specifier-qualifier list in each struct declaration and type name. Each list of
5115 type specifiers shall be one of the following sets (delimited by commas, when there is
5116 more than one set on a line); the type specifiers may occur in any order, possibly
5117 intermixed with the other declaration specifiers.
5118 <ul>
5119 <li> void
5120 <li> char
5121 <li> signed char
5122 <li> unsigned char
5123 <li> short, signed short, short int, or signed short int
5124 <li> unsigned short, or unsigned short int
5125 <li> int, signed, or signed int
5126 <!--page 112 -->
5127 <li> unsigned, or unsigned int
5128 <li> long, signed long, long int, or signed long int
5129 <li> unsigned long, or unsigned long int
5130 <li> long long, signed long long, long long int, or
5131 signed long long int
5132 <li> unsigned long long, or unsigned long long int
5133 <li> float
5134 <li> double
5135 <li> long double
5136 <li> _Bool
5137 <li> float _Complex
5138 <li> double _Complex
5139 <li> long double _Complex
5140 <li> struct or union specifier *
5141 <li> enum specifier
5142 <li> typedef name
5143 </ul>
5144 <p><!--para 3 -->
5145 The type specifier _Complex shall not be used if the implementation does not provide
5147 <h6>Semantics</h6>
5148 <p><!--para 4 -->
5149 Specifiers for structures, unions, and enumerations are discussed in <a href="#6.7.2.1">6.7.2.1</a> through
5150 <a href="#6.7.2.3">6.7.2.3</a>. Declarations of typedef names are discussed in <a href="#6.7.7">6.7.7</a>. The characteristics of the
5152 <p><!--para 5 -->
5153 Each of the comma-separated sets designates the same type, except that for bit-fields, it is
5154 implementation-defined whether the specifier int designates the same type as signed
5155 int or the same type as unsigned int.
5156 <p><b> Forward references</b>: enumeration specifiers (<a href="#6.7.2.2">6.7.2.2</a>), structure and union specifiers
5157 (<a href="#6.7.2.1">6.7.2.1</a>), tags (<a href="#6.7.2.3">6.7.2.3</a>), type definitions (<a href="#6.7.7">6.7.7</a>).
5162 <!--page 113 -->
5164 <h6>footnotes</h6>
5165 <p><small><a name="note104" href="#note104">104)</a> Freestanding implementations are not required to provide complex types. *
5166 </small>
5169 <h6>Syntax</h6>
5170 <p><!--para 1 -->
5171 <pre>
5172 struct-or-union-specifier:
5173 struct-or-union identifieropt { struct-declaration-list }
5174 struct-or-union identifier
5175 struct-or-union:
5176 struct
5177 union
5178 struct-declaration-list:
5179 struct-declaration
5180 struct-declaration-list struct-declaration
5181 struct-declaration:
5182 specifier-qualifier-list struct-declarator-list ;
5183 specifier-qualifier-list:
5184 type-specifier specifier-qualifier-listopt
5185 type-qualifier specifier-qualifier-listopt
5186 struct-declarator-list:
5187 struct-declarator
5188 struct-declarator-list , struct-declarator
5189 struct-declarator:
5190 declarator
5191 declaratoropt : constant-expression</pre>
5192 <h6>Constraints</h6>
5193 <p><!--para 2 -->
5194 A structure or union shall not contain a member with incomplete or function type (hence,
5195 a structure shall not contain an instance of itself, but may contain a pointer to an instance
5196 of itself), except that the last member of a structure with more than one named member
5197 may have incomplete array type; such a structure (and any union containing, possibly
5198 recursively, a member that is such a structure) shall not be a member of a structure or an
5199 element of an array.
5200 <p><!--para 3 -->
5201 The expression that specifies the width of a bit-field shall be an integer constant
5202 expression with a nonnegative value that does not exceed the width of an object of the
5203 type that would be specified were the colon and expression omitted. If the value is zero,
5204 the declaration shall have no declarator.
5205 <p><!--para 4 -->
5206 A bit-field shall have a type that is a qualified or unqualified version of _Bool, signed
5207 int, unsigned int, or some other implementation-defined type.
5208 <!--page 114 -->
5209 <h6>Semantics</h6>
5210 <p><!--para 5 -->
5211 As discussed in <a href="#6.2.5">6.2.5</a>, a structure is a type consisting of a sequence of members, whose
5212 storage is allocated in an ordered sequence, and a union is a type consisting of a sequence
5213 of members whose storage overlap.
5214 <p><!--para 6 -->
5215 Structure and union specifiers have the same form. The keywords struct and union
5216 indicate that the type being specified is, respectively, a structure type or a union type.
5217 <p><!--para 7 -->
5218 The presence of a struct-declaration-list in a struct-or-union-specifier declares a new type,
5219 within a translation unit. The struct-declaration-list is a sequence of declarations for the
5220 members of the structure or union. If the struct-declaration-list contains no named
5221 members, the behavior is undefined. The type is incomplete until after the } that
5222 terminates the list.
5223 <p><!--para 8 -->
5224 A member of a structure or union may have any object type other than a variably
5225 modified type.<sup><a href="#note105"><b>105)</b></a></sup> In addition, a member may be declared to consist of a specified
5226 number of bits (including a sign bit, if any). Such a member is called a bit-field;<sup><a href="#note106"><b>106)</b></a></sup> its
5227 width is preceded by a colon.
5228 <p><!--para 9 -->
5229 A bit-field is interpreted as a signed or unsigned integer type consisting of the specified
5230 number of bits.<sup><a href="#note107"><b>107)</b></a></sup> If the value 0 or 1 is stored into a nonzero-width bit-field of type
5231 _Bool, the value of the bit-field shall compare equal to the value stored.
5232 <p><!--para 10 -->
5233 An implementation may allocate any addressable storage unit large enough to hold a bit-
5234 field. If enough space remains, a bit-field that immediately follows another bit-field in a
5235 structure shall be packed into adjacent bits of the same unit. If insufficient space remains,
5236 whether a bit-field that does not fit is put into the next unit or overlaps adjacent units is
5237 implementation-defined. The order of allocation of bit-fields within a unit (high-order to
5238 low-order or low-order to high-order) is implementation-defined. The alignment of the
5239 addressable storage unit is unspecified.
5240 <p><!--para 11 -->
5241 A bit-field declaration with no declarator, but only a colon and a width, indicates an
5242 unnamed bit-field.<sup><a href="#note108"><b>108)</b></a></sup> As a special case, a bit-field structure member with a width of 0
5243 indicates that no further bit-field is to be packed into the unit in which the previous bit-
5244 field, if any, was placed.
5247 <!--page 115 -->
5248 <p><!--para 12 -->
5249 Each non-bit-field member of a structure or union object is aligned in an implementation-
5250 defined manner appropriate to its type.
5251 <p><!--para 13 -->
5252 Within a structure object, the non-bit-field members and the units in which bit-fields
5253 reside have addresses that increase in the order in which they are declared. A pointer to a
5254 structure object, suitably converted, points to its initial member (or if that member is a
5255 bit-field, then to the unit in which it resides), and vice versa. There may be unnamed
5256 padding within a structure object, but not at its beginning.
5257 <p><!--para 14 -->
5258 The size of a union is sufficient to contain the largest of its members. The value of at
5259 most one of the members can be stored in a union object at any time. A pointer to a
5260 union object, suitably converted, points to each of its members (or if a member is a bit-
5261 field, then to the unit in which it resides), and vice versa.
5262 <p><!--para 15 -->
5263 There may be unnamed padding at the end of a structure or union.
5264 <p><!--para 16 -->
5265 As a special case, the last element of a structure with more than one named member may
5266 have an incomplete array type; this is called a flexible array member. In most situations,
5267 the flexible array member is ignored. In particular, the size of the structure is as if the
5268 flexible array member were omitted except that it may have more trailing padding than
5269 the omission would imply. However, when a . (or ->) operator has a left operand that is
5270 (a pointer to) a structure with a flexible array member and the right operand names that
5271 member, it behaves as if that member were replaced with the longest array (with the same
5272 element type) that would not make the structure larger than the object being accessed; the
5273 offset of the array shall remain that of the flexible array member, even if this would differ
5274 from that of the replacement array. If this array would have no elements, it behaves as if
5275 it had one element but the behavior is undefined if any attempt is made to access that
5276 element or to generate a pointer one past it.
5277 <p><!--para 17 -->
5278 EXAMPLE After the declaration:
5279 <pre>
5280 struct s { int n; double d[]; };</pre>
5281 the structure struct s has a flexible array member d. A typical way to use this is:
5282 <pre>
5283 int m = /* some value */;
5284 struct s *p = malloc(sizeof (struct s) + sizeof (double [m]));</pre>
5285 and assuming that the call to malloc succeeds, the object pointed to by p behaves, for most purposes, as if
5286 p had been declared as:
5287 <pre>
5288 struct { int n; double d[m]; } *p;</pre>
5289 (there are circumstances in which this equivalence is broken; in particular, the offsets of member d might
5290 not be the same).
5291 <p><!--para 18 -->
5292 Following the above declaration:
5293 <!--page 116 -->
5294 <pre>
5295 struct s t1 = { 0 }; // valid
5297 t1.n = 4; // valid
5299 The initialization of t2 is invalid (and violates a constraint) because struct s is treated as if it did not
5300 contain member d. The assignment to t1.d[0] is probably undefined behavior, but it is possible that
5301 <pre>
5302 sizeof (struct s) >= offsetof(struct s, d) + sizeof (double)</pre>
5303 in which case the assignment would be legitimate. Nevertheless, it cannot appear in strictly conforming
5304 code.
5305 <p><!--para 19 -->
5306 After the further declaration:
5307 <pre>
5308 struct ss { int n; };</pre>
5309 the expressions:
5310 <pre>
5311 sizeof (struct s) >= sizeof (struct ss)
5312 sizeof (struct s) >= offsetof(struct s, d)</pre>
5313 are always equal to 1.
5314 <p><!--para 20 -->
5315 If sizeof (double) is 8, then after the following code is executed:
5316 <pre>
5317 struct s *s1;
5318 struct s *s2;
5319 s1 = malloc(sizeof (struct s) + 64);
5320 s2 = malloc(sizeof (struct s) + 46);</pre>
5321 and assuming that the calls to malloc succeed, the objects pointed to by s1 and s2 behave, for most
5322 purposes, as if the identifiers had been declared as:
5323 <p><!--para 21 -->
5324 <pre>
5325 struct { int n; double d[8]; } *s1;
5326 struct { int n; double d[5]; } *s2;</pre>
5327 Following the further successful assignments:
5328 <pre>
5329 s1 = malloc(sizeof (struct s) + 10);
5330 s2 = malloc(sizeof (struct s) + 6);</pre>
5331 they then behave as if the declarations were:
5332 <pre>
5333 struct { int n; double d[1]; } *s1, *s2;</pre>
5334 and:
5335 <p><!--para 22 -->
5336 <pre>
5337 double *dp;
5338 dp = &(s1->d[0]); // valid
5339 *dp = 42; // valid
5340 dp = &(s2->d[0]); // valid
5341 *dp = 42; // undefined behavior</pre>
5342 The assignment:
5343 <pre>
5344 *s1 = *s2;</pre>
5345 only copies the member n; if any of the array elements are within the first sizeof (struct s) bytes
5346 of the structure, they might be copied or simply overwritten with indeterminate values.
5349 <!--page 117 -->
5351 <h6>footnotes</h6>
5352 <p><small><a name="note105" href="#note105">105)</a> A structure or union can not contain a member with a variably modified type because member names
5354 </small>
5355 <p><small><a name="note106" href="#note106">106)</a> The unary & (address-of) operator cannot be applied to a bit-field object; thus, there are no pointers to
5356 or arrays of bit-field objects.
5357 </small>
5358 <p><small><a name="note107" href="#note107">107)</a> As specified in <a href="#6.7.2">6.7.2</a> above, if the actual type specifier used is int or a typedef-name defined as int,
5359 then it is implementation-defined whether the bit-field is signed or unsigned.
5360 </small>
5361 <p><small><a name="note108" href="#note108">108)</a> An unnamed bit-field structure member is useful for padding to conform to externally imposed
5362 layouts.
5363 </small>
5366 <h6>Syntax</h6>
5367 <p><!--para 1 -->
5368 <pre>
5369 enum-specifier:
5370 enum identifieropt { enumerator-list }
5371 enum identifieropt { enumerator-list , }
5372 enum identifier
5373 enumerator-list:
5374 enumerator
5375 enumerator-list , enumerator
5376 enumerator:
5377 enumeration-constant
5378 enumeration-constant = constant-expression</pre>
5379 <h6>Constraints</h6>
5380 <p><!--para 2 -->
5381 The expression that defines the value of an enumeration constant shall be an integer
5382 constant expression that has a value representable as an int.
5383 <h6>Semantics</h6>
5384 <p><!--para 3 -->
5385 The identifiers in an enumerator list are declared as constants that have type int and
5386 may appear wherever such are permitted.<sup><a href="#note109"><b>109)</b></a></sup> An enumerator with = defines its
5387 enumeration constant as the value of the constant expression. If the first enumerator has
5388 no =, the value of its enumeration constant is 0. Each subsequent enumerator with no =
5389 defines its enumeration constant as the value of the constant expression obtained by
5390 adding 1 to the value of the previous enumeration constant. (The use of enumerators with
5391 = may produce enumeration constants with values that duplicate other values in the same
5392 enumeration.) The enumerators of an enumeration are also known as its members.
5393 <p><!--para 4 -->
5394 Each enumerated type shall be compatible with char, a signed integer type, or an
5395 unsigned integer type. The choice of type is implementation-defined,<sup><a href="#note110"><b>110)</b></a></sup> but shall be
5396 capable of representing the values of all the members of the enumeration. The
5397 enumerated type is incomplete until after the } that terminates the list of enumerator
5398 declarations.
5403 <!--page 118 -->
5404 <p><!--para 5 -->
5405 EXAMPLE The following fragment:
5406 <pre>
5407 enum hue { chartreuse, burgundy, claret=20, winedark };
5408 enum hue col, *cp;
5409 col = claret;
5410 cp = &col;
5411 if (*cp != burgundy)
5412 /* ... */</pre>
5413 makes hue the tag of an enumeration, and then declares col as an object that has that type and cp as a
5414 pointer to an object that has that type. The enumerated values are in the set { 0, 1, 20, 21 }.
5418 <h6>footnotes</h6>
5419 <p><small><a name="note109" href="#note109">109)</a> Thus, the identifiers of enumeration constants declared in the same scope shall all be distinct from
5420 each other and from other identifiers declared in ordinary declarators.
5421 </small>
5422 <p><small><a name="note110" href="#note110">110)</a> An implementation may delay the choice of which integer type until all enumeration constants have
5423 been seen.
5424 </small>
5427 <h6>Constraints</h6>
5428 <p><!--para 1 -->
5429 A specific type shall have its content defined at most once.
5430 <p><!--para 2 -->
5431 Where two declarations that use the same tag declare the same type, they shall both use
5432 the same choice of struct, union, or enum.
5433 <p><!--para 3 -->
5434 A type specifier of the form
5435 <pre>
5436 enum identifier</pre>
5437 without an enumerator list shall only appear after the type it specifies is complete.
5438 <h6>Semantics</h6>
5439 <p><!--para 4 -->
5440 All declarations of structure, union, or enumerated types that have the same scope and
5441 use the same tag declare the same type. The type is incomplete<sup><a href="#note111"><b>111)</b></a></sup> until the closing brace
5442 of the list defining the content, and complete thereafter.
5443 <p><!--para 5 -->
5444 Two declarations of structure, union, or enumerated types which are in different scopes or
5445 use different tags declare distinct types. Each declaration of a structure, union, or
5446 enumerated type which does not include a tag declares a distinct type.
5447 <p><!--para 6 -->
5448 A type specifier of the form
5449 <pre>
5450 struct-or-union identifieropt { struct-declaration-list }</pre>
5451 or
5452 <pre>
5453 enum identifier { enumerator-list }</pre>
5454 or
5455 <pre>
5456 enum identifier { enumerator-list , }</pre>
5457 declares a structure, union, or enumerated type. The list defines the structure content,
5459 <!--page 119 -->
5460 union content, or enumeration content. If an identifier is provided,<sup><a href="#note112"><b>112)</b></a></sup> the type specifier
5461 also declares the identifier to be the tag of that type.
5462 <p><!--para 7 -->
5463 A declaration of the form
5464 <pre>
5465 struct-or-union identifier ;</pre>
5466 specifies a structure or union type and declares the identifier as a tag of that type.<sup><a href="#note113"><b>113)</b></a></sup>
5467 <p><!--para 8 -->
5468 If a type specifier of the form
5469 <pre>
5470 struct-or-union identifier</pre>
5471 occurs other than as part of one of the above forms, and no other declaration of the
5472 identifier as a tag is visible, then it declares an incomplete structure or union type, and
5473 declares the identifier as the tag of that type.113)
5474 <p><!--para 9 -->
5475 If a type specifier of the form
5476 <pre>
5477 struct-or-union identifier</pre>
5478 or
5479 <pre>
5480 enum identifier</pre>
5481 occurs other than as part of one of the above forms, and a declaration of the identifier as a
5482 tag is visible, then it specifies the same type as that other declaration, and does not
5483 redeclare the tag.
5484 <p><!--para 10 -->
5485 EXAMPLE 1 This mechanism allows declaration of a self-referential structure.
5486 <pre>
5487 struct tnode {
5488 int count;
5489 struct tnode *left, *right;
5490 };</pre>
5491 specifies a structure that contains an integer and two pointers to objects of the same type. Once this
5492 declaration has been given, the declaration
5493 <pre>
5494 struct tnode s, *sp;</pre>
5495 declares s to be an object of the given type and sp to be a pointer to an object of the given type. With
5496 these declarations, the expression sp->left refers to the left struct tnode pointer of the object to
5497 which sp points; the expression s.right->count designates the count member of the right struct
5498 tnode pointed to from s.
5499 <p><!--para 11 -->
5500 The following alternative formulation uses the typedef mechanism:
5505 <!--page 120 -->
5506 <pre>
5507 typedef struct tnode TNODE;
5508 struct tnode {
5509 int count;
5510 TNODE *left, *right;
5511 };
5512 TNODE s, *sp;</pre>
5514 <p><!--para 12 -->
5515 EXAMPLE 2 To illustrate the use of prior declaration of a tag to specify a pair of mutually referential
5516 structures, the declarations
5517 <pre>
5518 struct s1 { struct s2 *s2p; /* ... */ }; // D1
5519 struct s2 { struct s1 *s1p; /* ... */ }; // D2</pre>
5520 specify a pair of structures that contain pointers to each other. Note, however, that if s2 were already
5521 declared as a tag in an enclosing scope, the declaration D1 would refer to it, not to the tag s2 declared in
5522 D2. To eliminate this context sensitivity, the declaration
5523 <pre>
5524 struct s2;</pre>
5525 may be inserted ahead of D1. This declares a new tag s2 in the inner scope; the declaration D2 then
5526 completes the specification of the new type.
5528 <p><b> Forward references</b>: declarators (<a href="#6.7.5">6.7.5</a>), array declarators (<a href="#6.7.5.2">6.7.5.2</a>), type definitions
5531 <h6>footnotes</h6>
5532 <p><small><a name="note111" href="#note111">111)</a> An incomplete type may only by used when the size of an object of that type is not needed. It is not
5533 needed, for example, when a typedef name is declared to be a specifier for a structure or union, or
5534 when a pointer to or a function returning a structure or union is being declared. (See incomplete types
5535 in <a href="#6.2.5">6.2.5</a>.) The specification has to be complete before such a function is called or defined.
5536 </small>
5537 <p><small><a name="note112" href="#note112">112)</a> If there is no identifier, the type can, within the translation unit, only be referred to by the declaration
5538 of which it is a part. Of course, when the declaration is of a typedef name, subsequent declarations
5539 can make use of that typedef name to declare objects having the specified structure, union, or
5540 enumerated type.
5541 </small>
5542 <p><small><a name="note113" href="#note113">113)</a> A similar construction with enum does not exist.
5543 </small>
5546 <h6>Syntax</h6>
5547 <p><!--para 1 -->
5548 <pre>
5549 type-qualifier:
5550 const
5551 restrict
5552 volatile</pre>
5553 <h6>Constraints</h6>
5554 <p><!--para 2 -->
5555 Types other than pointer types derived from object or incomplete types shall not be
5556 restrict-qualified.
5557 <h6>Semantics</h6>
5558 <p><!--para 3 -->
5559 The properties associated with qualified types are meaningful only for expressions that
5561 <p><!--para 4 -->
5562 If the same qualifier appears more than once in the same specifier-qualifier-list, either
5563 directly or via one or more typedefs, the behavior is the same as if it appeared only
5564 once.
5569 <!--page 121 -->
5570 <p><!--para 5 -->
5571 If an attempt is made to modify an object defined with a const-qualified type through use
5572 of an lvalue with non-const-qualified type, the behavior is undefined. If an attempt is
5573 made to refer to an object defined with a volatile-qualified type through use of an lvalue
5574 with non-volatile-qualified type, the behavior is undefined.<sup><a href="#note115"><b>115)</b></a></sup>
5575 <p><!--para 6 -->
5576 An object that has volatile-qualified type may be modified in ways unknown to the
5577 implementation or have other unknown side effects. Therefore any expression referring
5578 to such an object shall be evaluated strictly according to the rules of the abstract machine,
5579 as described in <a href="#5.1.2.3">5.1.2.3</a>. Furthermore, at every sequence point the value last stored in the
5580 object shall agree with that prescribed by the abstract machine, except as modified by the
5581 unknown factors mentioned previously.<sup><a href="#note116"><b>116)</b></a></sup> What constitutes an access to an object that
5582 has volatile-qualified type is implementation-defined.
5583 <p><!--para 7 -->
5584 An object that is accessed through a restrict-qualified pointer has a special association
5585 with that pointer. This association, defined in <a href="#6.7.3.1">6.7.3.1</a> below, requires that all accesses to
5586 that object use, directly or indirectly, the value of that particular pointer.<sup><a href="#note117"><b>117)</b></a></sup> The intended
5587 use of the restrict qualifier (like the register storage class) is to promote
5588 optimization, and deleting all instances of the qualifier from all preprocessing translation
5589 units composing a conforming program does not change its meaning (i.e., observable
5590 behavior).
5591 <p><!--para 8 -->
5592 If the specification of an array type includes any type qualifiers, the element type is so-
5593 qualified, not the array type. If the specification of a function type includes any type
5595 <p><!--para 9 -->
5596 For two qualified types to be compatible, both shall have the identically qualified version
5597 of a compatible type; the order of type qualifiers within a list of specifiers or qualifiers
5598 does not affect the specified type.
5599 <p><!--para 10 -->
5600 EXAMPLE 1 An object declared
5601 <pre>
5602 extern const volatile int real_time_clock;</pre>
5603 may be modifiable by hardware, but cannot be assigned to, incremented, or decremented.
5608 <!--page 122 -->
5609 <p><!--para 11 -->
5610 EXAMPLE 2 The following declarations and expressions illustrate the behavior when type qualifiers
5611 modify an aggregate type:
5612 <pre>
5613 const struct s { int mem; } cs = { 1 };
5614 struct s ncs; // the object ncs is modifiable
5615 typedef int A[2][3];
5616 const A a = {{4, 5, 6}, {7, 8, 9}}; // array of array of const int
5617 int *pi;
5618 const int *pci;
5619 ncs = cs; // valid
5620 cs = ncs; // violates modifiable lvalue constraint for =
5621 pi = &ncs.mem; // valid
5622 pi = &cs.mem; // violates type constraints for =
5623 pci = &cs.mem; // valid
5624 pi = a[0]; // invalid: a[0] has type ''const int *''</pre>
5627 <h6>footnotes</h6>
5628 <p><small><a name="note114" href="#note114">114)</a> The implementation may place a const object that is not volatile in a read-only region of
5629 storage. Moreover, the implementation need not allocate storage for such an object if its address is
5630 never used.
5631 </small>
5632 <p><small><a name="note115" href="#note115">115)</a> This applies to those objects that behave as if they were defined with qualified types, even if they are
5633 never actually defined as objects in the program (such as an object at a memory-mapped input/output
5634 address).
5635 </small>
5636 <p><small><a name="note116" href="#note116">116)</a> A volatile declaration may be used to describe an object corresponding to a memory-mapped
5637 input/output port or an object accessed by an asynchronously interrupting function. Actions on
5638 objects so declared shall not be ''optimized out'' by an implementation or reordered except as
5639 permitted by the rules for evaluating expressions.
5640 </small>
5641 <p><small><a name="note117" href="#note117">117)</a> For example, a statement that assigns a value returned by malloc to a single pointer establishes this
5642 association between the allocated object and the pointer.
5643 </small>
5644 <p><small><a name="note118" href="#note118">118)</a> Both of these can occur through the use of typedefs.
5645 </small>
5648 <p><!--para 1 -->
5649 Let D be a declaration of an ordinary identifier that provides a means of designating an
5650 object P as a restrict-qualified pointer to type T.
5651 <p><!--para 2 -->
5652 If D appears inside a block and does not have storage class extern, let B denote the
5653 block. If D appears in the list of parameter declarations of a function definition, let B
5654 denote the associated block. Otherwise, let B denote the block of main (or the block of
5655 whatever function is called at program startup in a freestanding environment).
5656 <p><!--para 3 -->
5657 In what follows, a pointer expression E is said to be based on object P if (at some
5658 sequence point in the execution of B prior to the evaluation of E) modifying P to point to
5659 a copy of the array object into which it formerly pointed would change the value of E.<sup><a href="#note119"><b>119)</b></a></sup>
5660 Note that ''based'' is defined only for expressions with pointer types.
5661 <p><!--para 4 -->
5662 During each execution of B, let L be any lvalue that has &L based on P. If L is used to
5663 access the value of the object X that it designates, and X is also modified (by any means),
5664 then the following requirements apply: T shall not be const-qualified. Every other lvalue
5665 used to access the value of X shall also have its address based on P. Every access that
5666 modifies X shall be considered also to modify P, for the purposes of this subclause. If P
5667 is assigned the value of a pointer expression E that is based on another restricted pointer
5668 object P2, associated with block B2, then either the execution of B2 shall begin before
5669 the execution of B, or the execution of B2 shall end prior to the assignment. If these
5670 requirements are not met, then the behavior is undefined.
5671 <p><!--para 5 -->
5672 Here an execution of B means that portion of the execution of the program that would
5673 correspond to the lifetime of an object with scalar type and automatic storage duration
5675 <!--page 123 -->
5676 associated with B.
5677 <p><!--para 6 -->
5678 A translator is free to ignore any or all aliasing implications of uses of restrict.
5679 <p><!--para 7 -->
5680 EXAMPLE 1 The file scope declarations
5681 <pre>
5682 int * restrict a;
5683 int * restrict b;
5684 extern int c[];</pre>
5685 assert that if an object is accessed using one of a, b, or c, and that object is modified anywhere in the
5686 program, then it is never accessed using either of the other two.
5688 <p><!--para 8 -->
5689 EXAMPLE 2 The function parameter declarations in the following example
5690 <pre>
5691 void f(int n, int * restrict p, int * restrict q)
5692 {
5693 while (n-- > 0)
5694 *p++ = *q++;
5695 }</pre>
5696 assert that, during each execution of the function, if an object is accessed through one of the pointer
5697 parameters, then it is not also accessed through the other.
5698 <p><!--para 9 -->
5699 The benefit of the restrict qualifiers is that they enable a translator to make an effective dependence
5700 analysis of function f without examining any of the calls of f in the program. The cost is that the
5701 programmer has to examine all of those calls to ensure that none give undefined behavior. For example, the
5702 second call of f in g has undefined behavior because each of d[1] through d[49] is accessed through
5703 both p and q.
5704 <pre>
5705 void g(void)
5706 {
5707 extern int d[100];
5708 f(50, d + 50, d); // valid
5709 f(50, d + 1, d); // undefined behavior
5710 }</pre>
5712 <p><!--para 10 -->
5713 EXAMPLE 3 The function parameter declarations
5714 <pre>
5715 void h(int n, int * restrict p, int * restrict q, int * restrict r)
5716 {
5717 int i;
5718 for (i = 0; i < n; i++)
5719 p[i] = q[i] + r[i];
5720 }</pre>
5721 illustrate how an unmodified object can be aliased through two restricted pointers. In particular, if a and b
5722 are disjoint arrays, a call of the form h(100, a, b, b) has defined behavior, because array b is not
5723 modified within function h.
5725 <p><!--para 11 -->
5726 EXAMPLE 4 The rule limiting assignments between restricted pointers does not distinguish between a
5727 function call and an equivalent nested block. With one exception, only ''outer-to-inner'' assignments
5728 between restricted pointers declared in nested blocks have defined behavior.
5729 <!--page 124 -->
5730 <p><!--para 12 -->
5731 <pre>
5732 {
5733 int * restrict p1;
5734 int * restrict q1;
5735 p1 = q1; // undefined behavior
5736 {
5737 int * restrict p2 = p1; // valid
5738 int * restrict q2 = q1; // valid
5739 p1 = q2; // undefined behavior
5740 p2 = q2; // undefined behavior
5741 }
5742 }</pre>
5743 The one exception allows the value of a restricted pointer to be carried out of the block in which it (or, more
5744 precisely, the ordinary identifier used to designate it) is declared when that block finishes execution. For
5745 example, this permits new_vector to return a vector.
5746 <pre>
5747 typedef struct { int n; float * restrict v; } vector;
5748 vector new_vector(int n)
5749 {
5750 vector t;
5751 t.n = n;
5752 t.v = malloc(n * sizeof (float));
5753 return t;
5754 }</pre>
5757 <h6>footnotes</h6>
5758 <p><small><a name="note119" href="#note119">119)</a> In other words, E depends on the value of P itself rather than on the value of an object referenced
5759 indirectly through P. For example, if identifier p has type (int **restrict), then the pointer
5760 expressions p and p+1 are based on the restricted pointer object designated by p, but the pointer
5761 expressions *p and p[1] are not.
5762 </small>
5765 <h6>Syntax</h6>
5766 <p><!--para 1 -->
5767 <pre>
5768 function-specifier:
5769 inline</pre>
5770 <h6>Constraints</h6>
5771 <p><!--para 2 -->
5772 Function specifiers shall be used only in the declaration of an identifier for a function.
5773 <p><!--para 3 -->
5774 An inline definition of a function with external linkage shall not contain a definition of a
5775 modifiable object with static storage duration, and shall not contain a reference to an
5776 identifier with internal linkage.
5777 <p><!--para 4 -->
5778 In a hosted environment, the inline function specifier shall not appear in a declaration
5779 of main.
5780 <h6>Semantics</h6>
5781 <p><!--para 5 -->
5782 A function declared with an inline function specifier is an inline function. The
5783 function specifier may appear more than once; the behavior is the same as if it appeared
5784 only once. Making a function an inline function suggests that calls to the function be as
5785 fast as possible.<sup><a href="#note120"><b>120)</b></a></sup> The extent to which such suggestions are effective is
5787 <p><!--para 6 -->
5788 Any function with internal linkage can be an inline function. For a function with external
5789 linkage, the following restrictions apply: If a function is declared with an inline
5790 <!--page 125 -->
5791 function specifier, then it shall also be defined in the same translation unit. If all of the
5792 file scope declarations for a function in a translation unit include the inline function
5793 specifier without extern, then the definition in that translation unit is an inline
5794 definition. An inline definition does not provide an external definition for the function,
5795 and does not forbid an external definition in another translation unit. An inline definition
5796 provides an alternative to an external definition, which a translator may use to implement
5797 any call to the function in the same translation unit. It is unspecified whether a call to the
5798 function uses the inline definition or the external definition.<sup><a href="#note122"><b>122)</b></a></sup>
5799 <p><!--para 7 -->
5800 EXAMPLE The declaration of an inline function with external linkage can result in either an external
5801 definition, or a definition available for use only within the translation unit. A file scope declaration with
5802 extern creates an external definition. The following example shows an entire translation unit.
5803 <p><!--para 8 -->
5804 <pre>
5805 inline double fahr(double t)
5806 {
5807 return (9.0 * t) / 5.0 + 32.0;
5808 }
5809 inline double cels(double t)
5810 {
5811 return (5.0 * (t - 32.0)) / 9.0;
5812 }
5813 extern double fahr(double); // creates an external definition
5814 double convert(int is_fahr, double temp)
5815 {
5816 /* A translator may perform inline substitutions */
5817 return is_fahr ? cels(temp) : fahr(temp);
5818 }</pre>
5819 Note that the definition of fahr is an external definition because fahr is also declared with extern, but
5820 the definition of cels is an inline definition. Because cels has external linkage and is referenced, an
5821 external definition has to appear in another translation unit (see <a href="#6.9">6.9</a>); the inline definition and the external
5822 definition are distinct and either may be used for the call.
5827 <!--page 126 -->
5829 <h6>footnotes</h6>
5830 <p><small><a name="note120" href="#note120">120)</a> By using, for example, an alternative to the usual function call mechanism, such as ''inline
5831 substitution''. Inline substitution is not textual substitution, nor does it create a new function.
5832 Therefore, for example, the expansion of a macro used within the body of the function uses the
5833 definition it had at the point the function body appears, and not where the function is called; and
5834 identifiers refer to the declarations in scope where the body occurs. Likewise, the function has a
5835 single address, regardless of the number of inline definitions that occur in addition to the external
5836 definition.
5837 </small>
5838 <p><small><a name="note121" href="#note121">121)</a> For example, an implementation might never perform inline substitution, or might only perform inline
5839 substitutions to calls in the scope of an inline declaration.
5840 </small>
5841 <p><small><a name="note122" href="#note122">122)</a> Since an inline definition is distinct from the corresponding external definition and from any other
5842 corresponding inline definitions in other translation units, all corresponding objects with static storage
5843 duration are also distinct in each of the definitions.
5844 </small>
5847 <h6>Syntax</h6>
5848 <p><!--para 1 -->
5849 <pre>
5850 declarator:
5851 pointeropt direct-declarator
5852 direct-declarator:
5853 identifier
5854 ( declarator )
5855 direct-declarator [ type-qualifier-listopt assignment-expressionopt ]
5856 direct-declarator [ static type-qualifier-listopt assignment-expression ]
5857 direct-declarator [ type-qualifier-list static assignment-expression ]
5858 direct-declarator [ type-qualifier-listopt * ]
5859 direct-declarator ( parameter-type-list )
5860 direct-declarator ( identifier-listopt )
5861 pointer:
5862 * type-qualifier-listopt
5863 * type-qualifier-listopt pointer
5864 type-qualifier-list:
5865 type-qualifier
5866 type-qualifier-list type-qualifier
5867 parameter-type-list:
5868 parameter-list
5869 parameter-list , ...
5870 parameter-list:
5871 parameter-declaration
5872 parameter-list , parameter-declaration
5873 parameter-declaration:
5874 declaration-specifiers declarator
5875 declaration-specifiers abstract-declaratoropt
5876 identifier-list:
5877 identifier
5878 identifier-list , identifier</pre>
5879 <h6>Semantics</h6>
5880 <p><!--para 2 -->
5881 Each declarator declares one identifier, and asserts that when an operand of the same
5882 form as the declarator appears in an expression, it designates a function or object with the
5883 scope, storage duration, and type indicated by the declaration specifiers.
5884 <p><!--para 3 -->
5885 A full declarator is a declarator that is not part of another declarator. The end of a full
5886 declarator is a sequence point. If, in the nested sequence of declarators in a full
5887 <!--page 127 -->
5888 declarator, there is a declarator specifying a variable length array type, the type specified
5889 by the full declarator is said to be variably modified. Furthermore, any type derived by
5890 declarator type derivation from a variably modified type is itself variably modified.
5891 <p><!--para 4 -->
5892 In the following subclauses, consider a declaration
5893 <pre>
5894 T D1</pre>
5895 where T contains the declaration specifiers that specify a type T (such as int) and D1 is
5896 a declarator that contains an identifier ident. The type specified for the identifier ident in
5897 the various forms of declarator is described inductively using this notation.
5898 <p><!--para 5 -->
5899 If, in the declaration ''T D1'', D1 has the form
5900 <pre>
5901 identifier</pre>
5902 then the type specified for ident is T .
5903 <p><!--para 6 -->
5904 If, in the declaration ''T D1'', D1 has the form
5905 <pre>
5906 ( D )</pre>
5907 then ident has the type specified by the declaration ''T D''. Thus, a declarator in
5908 parentheses is identical to the unparenthesized declarator, but the binding of complicated
5909 declarators may be altered by parentheses.
5910 Implementation limits
5911 <p><!--para 7 -->
5912 As discussed in <a href="#5.2.4.1">5.2.4.1</a>, an implementation may limit the number of pointer, array, and
5913 function declarators that modify an arithmetic, structure, union, or incomplete type, either
5914 directly or via one or more typedefs.
5915 <p><b> Forward references</b>: array declarators (<a href="#6.7.5.2">6.7.5.2</a>), type definitions (<a href="#6.7.7">6.7.7</a>).
5918 <h6>Semantics</h6>
5919 <p><!--para 1 -->
5920 If, in the declaration ''T D1'', D1 has the form
5921 <pre>
5922 * type-qualifier-listopt D</pre>
5923 and the type specified for ident in the declaration ''T D'' is ''derived-declarator-type-list
5924 T '', then the type specified for ident is ''derived-declarator-type-list type-qualifier-list
5925 pointer to T ''. For each type qualifier in the list, ident is a so-qualified pointer.
5926 <p><!--para 2 -->
5927 For two pointer types to be compatible, both shall be identically qualified and both shall
5928 be pointers to compatible types.
5929 <p><!--para 3 -->
5930 EXAMPLE The following pair of declarations demonstrates the difference between a ''variable pointer
5931 to a constant value'' and a ''constant pointer to a variable value''.
5932 <!--page 128 -->
5933 <pre>
5934 const int *ptr_to_constant;
5935 int *const constant_ptr;</pre>
5936 The contents of any object pointed to by ptr_to_constant shall not be modified through that pointer,
5937 but ptr_to_constant itself may be changed to point to another object. Similarly, the contents of the
5938 int pointed to by constant_ptr may be modified, but constant_ptr itself shall always point to the
5939 same location.
5940 <p><!--para 4 -->
5941 The declaration of the constant pointer constant_ptr may be clarified by including a definition for the
5942 type ''pointer to int''.
5943 <pre>
5944 typedef int *int_ptr;
5945 const int_ptr constant_ptr;</pre>
5946 declares constant_ptr as an object that has type ''const-qualified pointer to int''.
5950 <h6>Constraints</h6>
5951 <p><!--para 1 -->
5952 In addition to optional type qualifiers and the keyword static, the [ and ] may delimit
5953 an expression or *. If they delimit an expression (which specifies the size of an array), the
5954 expression shall have an integer type. If the expression is a constant expression, it shall
5955 have a value greater than zero. The element type shall not be an incomplete or function
5956 type. The optional type qualifiers and the keyword static shall appear only in a
5957 declaration of a function parameter with an array type, and then only in the outermost
5958 array type derivation.
5959 <p><!--para 2 -->
5960 An ordinary identifier (as defined in <a href="#6.2.3">6.2.3</a>) that has a variably modified type shall have
5961 either block scope and no linkage or function prototype scope. If an identifier is declared
5962 to be an object with static storage duration, it shall not have a variable length array type.
5963 <h6>Semantics</h6>
5964 <p><!--para 3 -->
5965 If, in the declaration ''T D1'', D1 has one of the forms:
5966 <pre>
5967 D[ type-qualifier-listopt assignment-expressionopt ]
5968 D[ static type-qualifier-listopt assignment-expression ]
5969 D[ type-qualifier-list static assignment-expression ]
5970 D[ type-qualifier-listopt * ]</pre>
5971 and the type specified for ident in the declaration ''T D'' is ''derived-declarator-type-list
5972 T '', then the type specified for ident is ''derived-declarator-type-list array of T ''.<sup><a href="#note123"><b>123)</b></a></sup>
5973 (See <a href="#6.7.5.3">6.7.5.3</a> for the meaning of the optional type qualifiers and the keyword static.)
5974 <p><!--para 4 -->
5975 If the size is not present, the array type is an incomplete type. If the size is * instead of
5976 being an expression, the array type is a variable length array type of unspecified size,
5977 which can only be used in declarations with function prototype scope;<sup><a href="#note124"><b>124)</b></a></sup> such arrays are
5978 nonetheless complete types. If the size is an integer constant expression and the element
5980 <!--page 129 -->
5981 type has a known constant size, the array type is not a variable length array type;
5982 otherwise, the array type is a variable length array type.
5983 <p><!--para 5 -->
5984 If the size is an expression that is not an integer constant expression: if it occurs in a
5985 declaration at function prototype scope, it is treated as if it were replaced by *; otherwise,
5986 each time it is evaluated it shall have a value greater than zero. The size of each instance
5987 of a variable length array type does not change during its lifetime. Where a size
5988 expression is part of the operand of a sizeof operator and changing the value of the
5989 size expression would not affect the result of the operator, it is unspecified whether or not
5990 the size expression is evaluated.
5991 <p><!--para 6 -->
5992 For two array types to be compatible, both shall have compatible element types, and if
5993 both size specifiers are present, and are integer constant expressions, then both size
5994 specifiers shall have the same constant value. If the two array types are used in a context
5995 which requires them to be compatible, it is undefined behavior if the two size specifiers
5996 evaluate to unequal values.
5997 <p><!--para 7 -->
5998 EXAMPLE 1
5999 <pre>
6000 float fa[11], *afp[17];</pre>
6001 declares an array of float numbers and an array of pointers to float numbers.
6003 <p><!--para 8 -->
6004 EXAMPLE 2 Note the distinction between the declarations
6005 <pre>
6006 extern int *x;
6007 extern int y[];</pre>
6008 The first declares x to be a pointer to int; the second declares y to be an array of int of unspecified size
6009 (an incomplete type), the storage for which is defined elsewhere.
6011 <p><!--para 9 -->
6012 EXAMPLE 3 The following declarations demonstrate the compatibility rules for variably modified types.
6013 <pre>
6014 extern int n;
6015 extern int m;
6016 void fcompat(void)
6017 {
6018 int a[n][6][m];
6019 int (*p)[4][n+1];
6020 int c[n][n][6][m];
6021 int (*r)[n][n][n+1];
6022 p = a; // invalid: not compatible because 4 != 6
6023 r = c; // compatible, but defined behavior only if
6024 // n == 6 and m == n+1
6025 }</pre>
6030 <!--page 130 -->
6031 <p><!--para 10 -->
6032 EXAMPLE 4 All declarations of variably modified (VM) types have to be at either block scope or
6033 function prototype scope. Array objects declared with the static or extern storage-class specifier
6034 cannot have a variable length array (VLA) type. However, an object declared with the static storage-
6035 class specifier can have a VM type (that is, a pointer to a VLA type). Finally, all identifiers declared with a
6036 VM type have to be ordinary identifiers and cannot, therefore, be members of structures or unions.
6037 <pre>
6038 extern int n;
6039 int A[n]; // invalid: file scope VLA
6040 extern int (*p2)[n]; // invalid: file scope VM
6041 int B[100]; // valid: file scope but not VM
6042 void fvla(int m, int C[m][m]); // valid: VLA with prototype scope
6043 void fvla(int m, int C[m][m]) // valid: adjusted to auto pointer to VLA
6044 {
6045 typedef int VLA[m][m]; // valid: block scope typedef VLA
6046 struct tag {
6047 int (*y)[n]; // invalid: y not ordinary identifier
6048 int z[n]; // invalid: z not ordinary identifier
6049 };
6050 int D[m]; // valid: auto VLA
6051 static int E[m]; // invalid: static block scope VLA
6052 extern int F[m]; // invalid: F has linkage and is VLA
6053 int (*s)[m]; // valid: auto pointer to VLA
6054 extern int (*r)[m]; // invalid: r has linkage and points to VLA
6055 static int (*q)[m] = &B; // valid: q is a static block pointer to VLA
6056 }</pre>
6058 <p><b> Forward references</b>: function declarators (<a href="#6.7.5.3">6.7.5.3</a>), function definitions (<a href="#6.9.1">6.9.1</a>),
6061 <h6>footnotes</h6>
6062 <p><small><a name="note123" href="#note123">123)</a> When several ''array of'' specifications are adjacent, a multidimensional array is declared.
6063 </small>
6064 <p><small><a name="note124" href="#note124">124)</a> Thus, * can be used only in function declarations that are not definitions (see <a href="#6.7.5.3">6.7.5.3</a>).
6065 </small>
6067 <h5><a name="6.7.5.3" href="#6.7.5.3">6.7.5.3 Function declarators (including prototypes)</a></h5>
6068 <h6>Constraints</h6>
6069 <p><!--para 1 -->
6070 A function declarator shall not specify a return type that is a function type or an array
6071 type.
6072 <p><!--para 2 -->
6073 The only storage-class specifier that shall occur in a parameter declaration is register.
6074 <p><!--para 3 -->
6075 An identifier list in a function declarator that is not part of a definition of that function
6076 shall be empty.
6077 <p><!--para 4 -->
6078 After adjustment, the parameters in a parameter type list in a function declarator that is
6079 part of a definition of that function shall not have incomplete type.
6080 <h6>Semantics</h6>
6081 <p><!--para 5 -->
6082 If, in the declaration ''T D1'', D1 has the form
6083 <pre>
6084 D( parameter-type-list )</pre>
6085 or
6086 <!--page 131 -->
6087 <pre>
6088 D( identifier-listopt )</pre>
6089 and the type specified for ident in the declaration ''T D'' is ''derived-declarator-type-list
6090 T '', then the type specified for ident is ''derived-declarator-type-list function returning
6091 T ''.
6092 <p><!--para 6 -->
6093 A parameter type list specifies the types of, and may declare identifiers for, the
6094 parameters of the function.
6095 <p><!--para 7 -->
6096 A declaration of a parameter as ''array of type'' shall be adjusted to ''qualified pointer to
6097 type'', where the type qualifiers (if any) are those specified within the [ and ] of the
6098 array type derivation. If the keyword static also appears within the [ and ] of the
6099 array type derivation, then for each call to the function, the value of the corresponding
6100 actual argument shall provide access to the first element of an array with at least as many
6101 elements as specified by the size expression.
6102 <p><!--para 8 -->
6103 A declaration of a parameter as ''function returning type'' shall be adjusted to ''pointer to
6105 <p><!--para 9 -->
6106 If the list terminates with an ellipsis (, ...), no information about the number or types
6108 <p><!--para 10 -->
6109 The special case of an unnamed parameter of type void as the only item in the list
6110 specifies that the function has no parameters.
6111 <p><!--para 11 -->
6112 If, in a parameter declaration, an identifier can be treated either as a typedef name or as a
6113 parameter name, it shall be taken as a typedef name.
6114 <p><!--para 12 -->
6115 If the function declarator is not part of a definition of that function, parameters may have
6116 incomplete type and may use the [*] notation in their sequences of declarator specifiers
6117 to specify variable length array types.
6118 <p><!--para 13 -->
6119 The storage-class specifier in the declaration specifiers for a parameter declaration, if
6120 present, is ignored unless the declared parameter is one of the members of the parameter
6121 type list for a function definition.
6122 <p><!--para 14 -->
6123 An identifier list declares only the identifiers of the parameters of the function. An empty
6124 list in a function declarator that is part of a definition of that function specifies that the
6125 function has no parameters. The empty list in a function declarator that is not part of a
6126 definition of that function specifies that no information about the number or types of the
6128 <p><!--para 15 -->
6129 For two function types to be compatible, both shall specify compatible return types.<sup><a href="#note127"><b>127)</b></a></sup>
6132 <!--page 132 -->
6133 Moreover, the parameter type lists, if both are present, shall agree in the number of
6134 parameters and in use of the ellipsis terminator; corresponding parameters shall have
6135 compatible types. If one type has a parameter type list and the other type is specified by a
6136 function declarator that is not part of a function definition and that contains an empty
6137 identifier list, the parameter list shall not have an ellipsis terminator and the type of each
6138 parameter shall be compatible with the type that results from the application of the
6139 default argument promotions. If one type has a parameter type list and the other type is
6140 specified by a function definition that contains a (possibly empty) identifier list, both shall
6141 agree in the number of parameters, and the type of each prototype parameter shall be
6142 compatible with the type that results from the application of the default argument
6143 promotions to the type of the corresponding identifier. (In the determination of type
6144 compatibility and of a composite type, each parameter declared with function or array
6145 type is taken as having the adjusted type and each parameter declared with qualified type
6146 is taken as having the unqualified version of its declared type.)
6147 <p><!--para 16 -->
6148 EXAMPLE 1 The declaration
6149 <pre>
6150 int f(void), *fip(), (*pfi)();</pre>
6151 declares a function f with no parameters returning an int, a function fip with no parameter specification
6152 returning a pointer to an int, and a pointer pfi to a function with no parameter specification returning an
6153 int. It is especially useful to compare the last two. The binding of *fip() is *(fip()), so that the
6154 declaration suggests, and the same construction in an expression requires, the calling of a function fip,
6155 and then using indirection through the pointer result to yield an int. In the declarator (*pfi)(), the
6156 extra parentheses are necessary to indicate that indirection through a pointer to a function yields a function
6157 designator, which is then used to call the function; it returns an int.
6158 <p><!--para 17 -->
6159 If the declaration occurs outside of any function, the identifiers have file scope and external linkage. If the
6160 declaration occurs inside a function, the identifiers of the functions f and fip have block scope and either
6161 internal or external linkage (depending on what file scope declarations for these identifiers are visible), and
6162 the identifier of the pointer pfi has block scope and no linkage.
6164 <p><!--para 18 -->
6165 EXAMPLE 2 The declaration
6166 <pre>
6167 int (*apfi[3])(int *x, int *y);</pre>
6168 declares an array apfi of three pointers to functions returning int. Each of these functions has two
6169 parameters that are pointers to int. The identifiers x and y are declared for descriptive purposes only and
6170 go out of scope at the end of the declaration of apfi.
6172 <p><!--para 19 -->
6173 EXAMPLE 3 The declaration
6174 <pre>
6175 int (*fpfi(int (*)(long), int))(int, ...);</pre>
6176 declares a function fpfi that returns a pointer to a function returning an int. The function fpfi has two
6177 parameters: a pointer to a function returning an int (with one parameter of type long int), and an int.
6178 The pointer returned by fpfi points to a function that has one int parameter and accepts zero or more
6179 additional arguments of any type.
6180 <!--page 133 -->
6181 <p><!--para 20 -->
6182 EXAMPLE 4 The following prototype has a variably modified parameter.
6183 <pre>
6184 void addscalar(int n, int m,
6185 double a[n][n*m+300], double x);
6186 int main()
6187 {
6188 double b[4][308];
6190 return 0;
6191 }
6192 void addscalar(int n, int m,
6193 double a[n][n*m+300], double x)
6194 {
6195 for (int i = 0; i < n; i++)
6196 for (int j = 0, k = n*m+300; j < k; j++)
6197 // a is a pointer to a VLA with n*m+300 elements
6198 a[i][j] += x;
6199 }</pre>
6201 <p><!--para 21 -->
6202 EXAMPLE 5 The following are all compatible function prototype declarators.
6203 <pre>
6204 double maximum(int n, int m, double a[n][m]);
6205 double maximum(int n, int m, double a[*][*]);
6206 double maximum(int n, int m, double a[ ][*]);
6207 double maximum(int n, int m, double a[ ][m]);</pre>
6208 as are:
6209 <pre>
6210 void f(double (* restrict a)[5]);
6211 void f(double a[restrict][5]);
6212 void f(double a[restrict 3][5]);
6213 void f(double a[restrict static 3][5]);</pre>
6214 (Note that the last declaration also specifies that the argument corresponding to a in any call to f must be a
6215 non-null pointer to the first of at least three arrays of 5 doubles, which the others do not.)
6217 <p><b> Forward references</b>: function definitions (<a href="#6.9.1">6.9.1</a>), type names (<a href="#6.7.6">6.7.6</a>).
6218 <!--page 134 -->
6220 <h6>footnotes</h6>
6221 <p><small><a name="note125" href="#note125">125)</a> The macros defined in the <a href="#7.15"><stdarg.h></a> header (<a href="#7.15">7.15</a>) may be used to access arguments that
6222 correspond to the ellipsis.
6223 </small>
6224 <p><small><a name="note126" href="#note126">126)</a> See ''future language directions'' (<a href="#6.11.6">6.11.6</a>).
6225 </small>
6226 <p><small><a name="note127" href="#note127">127)</a> If both function types are ''old style'', parameter types are not compared.
6227 </small>
6230 <h6>Syntax</h6>
6231 <p><!--para 1 -->
6232 <pre>
6233 type-name:
6234 specifier-qualifier-list abstract-declaratoropt
6235 abstract-declarator:
6236 pointer
6237 pointeropt direct-abstract-declarator
6238 direct-abstract-declarator:
6239 ( abstract-declarator )
6240 direct-abstract-declaratoropt [ type-qualifier-listopt
6241 assignment-expressionopt ]
6242 direct-abstract-declaratoropt [ static type-qualifier-listopt
6243 assignment-expression ]
6244 direct-abstract-declaratoropt [ type-qualifier-list static
6245 assignment-expression ]
6246 direct-abstract-declaratoropt [ * ]
6247 direct-abstract-declaratoropt ( parameter-type-listopt )</pre>
6248 <h6>Semantics</h6>
6249 <p><!--para 2 -->
6250 In several contexts, it is necessary to specify a type. This is accomplished using a type
6251 name, which is syntactically a declaration for a function or an object of that type that
6253 <p><!--para 3 -->
6254 EXAMPLE The constructions
6255 <pre>
6256 (a) int
6257 (b) int *
6258 (c) int *[3]
6259 (d) int (*)[3]
6260 (e) int (*)[*]
6261 (f) int *()
6262 (g) int (*)(void)
6263 (h) int (*const [])(unsigned int, ...)</pre>
6264 name respectively the types (a) int, (b) pointer to int, (c) array of three pointers to int, (d) pointer to an
6265 array of three ints, (e) pointer to a variable length array of an unspecified number of ints, (f) function
6266 with no parameter specification returning a pointer to int, (g) pointer to function with no parameters
6267 returning an int, and (h) array of an unspecified number of constant pointers to functions, each with one
6268 parameter that has type unsigned int and an unspecified number of other parameters, returning an
6269 int.
6274 <!--page 135 -->
6276 <h6>footnotes</h6>
6277 <p><small><a name="note128" href="#note128">128)</a> As indicated by the syntax, empty parentheses in a type name are interpreted as ''function with no
6278 parameter specification'', rather than redundant parentheses around the omitted identifier.
6279 </small>
6282 <h6>Syntax</h6>
6283 <p><!--para 1 -->
6284 <pre>
6285 typedef-name:
6286 identifier</pre>
6287 <h6>Constraints</h6>
6288 <p><!--para 2 -->
6289 If a typedef name specifies a variably modified type then it shall have block scope.
6290 <h6>Semantics</h6>
6291 <p><!--para 3 -->
6292 In a declaration whose storage-class specifier is typedef, each declarator defines an
6293 identifier to be a typedef name that denotes the type specified for the identifier in the way
6294 described in <a href="#6.7.5">6.7.5</a>. Any array size expressions associated with variable length array
6295 declarators are evaluated each time the declaration of the typedef name is reached in the
6296 order of execution. A typedef declaration does not introduce a new type, only a
6297 synonym for the type so specified. That is, in the following declarations:
6298 <pre>
6299 typedef T type_ident;
6300 type_ident D;</pre>
6301 type_ident is defined as a typedef name with the type specified by the declaration
6302 specifiers in T (known as T ), and the identifier in D has the type ''derived-declarator-
6303 type-list T '' where the derived-declarator-type-list is specified by the declarators of D. A
6304 typedef name shares the same name space as other identifiers declared in ordinary
6305 declarators.
6306 <p><!--para 4 -->
6307 EXAMPLE 1 After
6308 <pre>
6309 typedef int MILES, KLICKSP();
6310 typedef struct { double hi, lo; } range;</pre>
6311 the constructions
6312 <pre>
6313 MILES distance;
6314 extern KLICKSP *metricp;
6315 range x;
6316 range z, *zp;</pre>
6317 are all valid declarations. The type of distance is int, that of metricp is ''pointer to function with no
6318 parameter specification returning int'', and that of x and z is the specified structure; zp is a pointer to
6319 such a structure. The object distance has a type compatible with any other int object.
6321 <p><!--para 5 -->
6322 EXAMPLE 2 After the declarations
6323 <pre>
6324 typedef struct s1 { int x; } t1, *tp1;
6325 typedef struct s2 { int x; } t2, *tp2;</pre>
6326 type t1 and the type pointed to by tp1 are compatible. Type t1 is also compatible with type struct
6327 s1, but not compatible with the types struct s2, t2, the type pointed to by tp2, or int.
6328 <!--page 136 -->
6329 <p><!--para 6 -->
6330 EXAMPLE 3 The following obscure constructions
6331 <pre>
6332 typedef signed int t;
6333 typedef int plain;
6334 struct tag {
6335 unsigned t:4;
6336 const t:5;
6337 plain r:5;
6338 };</pre>
6339 declare a typedef name t with type signed int, a typedef name plain with type int, and a structure
6340 with three bit-field members, one named t that contains values in the range [0, 15], an unnamed const-
6341 qualified bit-field which (if it could be accessed) would contain values in either the range [-15, +15] or
6342 [-16, +15], and one named r that contains values in one of the ranges [0, 31], [-15, +15], or [-16, +15].
6343 (The choice of range is implementation-defined.) The first two bit-field declarations differ in that
6344 unsigned is a type specifier (which forces t to be the name of a structure member), while const is a
6345 type qualifier (which modifies t which is still visible as a typedef name). If these declarations are followed
6346 in an inner scope by
6347 <pre>
6348 t f(t (t));
6349 long t;</pre>
6350 then a function f is declared with type ''function returning signed int with one unnamed parameter
6351 with type pointer to function returning signed int with one unnamed parameter with type signed
6352 int'', and an identifier t with type long int.
6354 <p><!--para 7 -->
6355 EXAMPLE 4 On the other hand, typedef names can be used to improve code readability. All three of the
6356 following declarations of the signal function specify exactly the same type, the first without making use
6357 of any typedef names.
6358 <pre>
6359 typedef void fv(int), (*pfv)(int);
6360 void (*signal(int, void (*)(int)))(int);
6361 fv *signal(int, fv *);
6362 pfv signal(int, pfv);</pre>
6364 <p><!--para 8 -->
6365 EXAMPLE 5 If a typedef name denotes a variable length array type, the length of the array is fixed at the
6366 time the typedef name is defined, not each time it is used:
6367 <!--page 137 -->
6368 <pre>
6369 void copyt(int n)
6370 {
6371 typedef int B[n]; // B is n ints, n evaluated now
6372 n += 1;
6373 B a; // a is n ints, n without += 1
6374 int b[n]; // a and b are different sizes
6375 for (int i = 1; i < n; i++)
6376 a[i-1] = b[i];
6377 }</pre>
6380 <h6>Syntax</h6>
6381 <p><!--para 1 -->
6382 <pre>
6383 initializer:
6384 assignment-expression
6385 { initializer-list }
6386 { initializer-list , }
6387 initializer-list:
6388 designationopt initializer
6389 initializer-list , designationopt initializer
6390 designation:
6391 designator-list =
6392 designator-list:
6393 designator
6394 designator-list designator
6395 designator:
6396 [ constant-expression ]
6397 . identifier</pre>
6398 <h6>Constraints</h6>
6399 <p><!--para 2 -->
6400 No initializer shall attempt to provide a value for an object not contained within the entity
6401 being initialized.
6402 <p><!--para 3 -->
6403 The type of the entity to be initialized shall be an array of unknown size or an object type
6404 that is not a variable length array type.
6405 <p><!--para 4 -->
6406 All the expressions in an initializer for an object that has static storage duration shall be
6407 constant expressions or string literals.
6408 <p><!--para 5 -->
6409 If the declaration of an identifier has block scope, and the identifier has external or
6410 internal linkage, the declaration shall have no initializer for the identifier.
6411 <p><!--para 6 -->
6412 If a designator has the form
6413 <pre>
6414 [ constant-expression ]</pre>
6415 then the current object (defined below) shall have array type and the expression shall be
6416 an integer constant expression. If the array is of unknown size, any nonnegative value is
6417 valid.
6418 <p><!--para 7 -->
6419 If a designator has the form
6420 <pre>
6421 . identifier</pre>
6422 then the current object (defined below) shall have structure or union type and the
6423 identifier shall be the name of a member of that type.
6424 <!--page 138 -->
6425 <h6>Semantics</h6>
6426 <p><!--para 8 -->
6427 An initializer specifies the initial value stored in an object.
6428 <p><!--para 9 -->
6429 Except where explicitly stated otherwise, for the purposes of this subclause unnamed
6430 members of objects of structure and union type do not participate in initialization.
6431 Unnamed members of structure objects have indeterminate value even after initialization.
6432 <p><!--para 10 -->
6433 If an object that has automatic storage duration is not initialized explicitly, its value is
6434 indeterminate. If an object that has static storage duration is not initialized explicitly,
6435 then:
6436 <ul>
6437 <li> if it has pointer type, it is initialized to a null pointer;
6438 <li> if it has arithmetic type, it is initialized to (positive or unsigned) zero;
6439 <li> if it is an aggregate, every member is initialized (recursively) according to these rules;
6440 <li> if it is a union, the first named member is initialized (recursively) according to these
6441 rules.
6442 </ul>
6443 <p><!--para 11 -->
6444 The initializer for a scalar shall be a single expression, optionally enclosed in braces. The
6445 initial value of the object is that of the expression (after conversion); the same type
6446 constraints and conversions as for simple assignment apply, taking the type of the scalar
6447 to be the unqualified version of its declared type.
6448 <p><!--para 12 -->
6449 The rest of this subclause deals with initializers for objects that have aggregate or union
6450 type.
6451 <p><!--para 13 -->
6452 The initializer for a structure or union object that has automatic storage duration shall be
6453 either an initializer list as described below, or a single expression that has compatible
6454 structure or union type. In the latter case, the initial value of the object, including
6455 unnamed members, is that of the expression.
6456 <p><!--para 14 -->
6457 An array of character type may be initialized by a character string literal, optionally
6458 enclosed in braces. Successive characters of the character string literal (including the
6459 terminating null character if there is room or if the array is of unknown size) initialize the
6460 elements of the array.
6461 <p><!--para 15 -->
6462 An array with element type compatible with wchar_t may be initialized by a wide
6463 string literal, optionally enclosed in braces. Successive wide characters of the wide string
6464 literal (including the terminating null wide character if there is room or if the array is of
6465 unknown size) initialize the elements of the array.
6466 <p><!--para 16 -->
6467 Otherwise, the initializer for an object that has aggregate or union type shall be a brace-
6468 enclosed list of initializers for the elements or named members.
6469 <p><!--para 17 -->
6470 Each brace-enclosed initializer list has an associated current object. When no
6471 designations are present, subobjects of the current object are initialized in order according
6472 to the type of the current object: array elements in increasing subscript order, structure
6473 <!--page 139 -->
6474 members in declaration order, and the first named member of a union.<sup><a href="#note129"><b>129)</b></a></sup> In contrast, a
6475 designation causes the following initializer to begin initialization of the subobject
6476 described by the designator. Initialization then continues forward in order, beginning
6477 with the next subobject after that described by the designator.<sup><a href="#note130"><b>130)</b></a></sup>
6478 <p><!--para 18 -->
6479 Each designator list begins its description with the current object associated with the
6480 closest surrounding brace pair. Each item in the designator list (in order) specifies a
6481 particular member of its current object and changes the current object for the next
6482 designator (if any) to be that member.<sup><a href="#note131"><b>131)</b></a></sup> The current object that results at the end of the
6483 designator list is the subobject to be initialized by the following initializer.
6484 <p><!--para 19 -->
6485 The initialization shall occur in initializer list order, each initializer provided for a
6486 particular subobject overriding any previously listed initializer for the same subobject;<sup><a href="#note132"><b>132)</b></a></sup>
6487 all subobjects that are not initialized explicitly shall be initialized implicitly the same as
6488 objects that have static storage duration.
6489 <p><!--para 20 -->
6490 If the aggregate or union contains elements or members that are aggregates or unions,
6491 these rules apply recursively to the subaggregates or contained unions. If the initializer of
6492 a subaggregate or contained union begins with a left brace, the initializers enclosed by
6493 that brace and its matching right brace initialize the elements or members of the
6494 subaggregate or the contained union. Otherwise, only enough initializers from the list are
6495 taken to account for the elements or members of the subaggregate or the first member of
6496 the contained union; any remaining initializers are left to initialize the next element or
6497 member of the aggregate of which the current subaggregate or contained union is a part.
6498 <p><!--para 21 -->
6499 If there are fewer initializers in a brace-enclosed list than there are elements or members
6500 of an aggregate, or fewer characters in a string literal used to initialize an array of known
6501 size than there are elements in the array, the remainder of the aggregate shall be
6502 initialized implicitly the same as objects that have static storage duration.
6503 <p><!--para 22 -->
6504 If an array of unknown size is initialized, its size is determined by the largest indexed
6505 element with an explicit initializer. At the end of its initializer list, the array no longer
6506 has incomplete type.
6510 <!--page 140 -->
6511 <p><!--para 23 -->
6512 The order in which any side effects occur among the initialization list expressions is
6514 <p><!--para 24 -->
6515 EXAMPLE 1 Provided that <a href="#7.3"><complex.h></a> has been #included, the declarations
6516 <pre>
6518 double complex c = 5 + 3 * I;</pre>
6519 define and initialize i with the value 3 and c with the value 5.0 + i3.0.
6521 <p><!--para 25 -->
6522 EXAMPLE 2 The declaration
6523 <pre>
6524 int x[] = { 1, 3, 5 };</pre>
6525 defines and initializes x as a one-dimensional array object that has three elements, as no size was specified
6526 and there are three initializers.
6528 <p><!--para 26 -->
6529 EXAMPLE 3 The declaration
6530 <pre>
6531 int y[4][3] = {
6532 { 1, 3, 5 },
6533 { 2, 4, 6 },
6534 { 3, 5, 7 },
6535 };</pre>
6536 is a definition with a fully bracketed initialization: 1, 3, and 5 initialize the first row of y (the array object
6537 y[0]), namely y[0][0], y[0][1], and y[0][2]. Likewise the next two lines initialize y[1] and
6538 y[2]. The initializer ends early, so y[3] is initialized with zeros. Precisely the same effect could have
6539 been achieved by
6540 <pre>
6541 int y[4][3] = {
6542 1, 3, 5, 2, 4, 6, 3, 5, 7
6543 };</pre>
6544 The initializer for y[0] does not begin with a left brace, so three items from the list are used. Likewise the
6545 next three are taken successively for y[1] and y[2].
6547 <p><!--para 27 -->
6548 EXAMPLE 4 The declaration
6549 <pre>
6550 int z[4][3] = {
6551 { 1 }, { 2 }, { 3 }, { 4 }
6552 };</pre>
6553 initializes the first column of z as specified and initializes the rest with zeros.
6555 <p><!--para 28 -->
6556 EXAMPLE 5 The declaration
6557 <pre>
6558 struct { int a[3], b; } w[] = { { 1 }, 2 };</pre>
6559 is a definition with an inconsistently bracketed initialization. It defines an array with two element
6560 structures: w[0].a[0] is 1 and w[1].a[0] is 2; all the other elements are zero.
6565 <!--page 141 -->
6566 <p><!--para 29 -->
6567 EXAMPLE 6 The declaration
6568 <pre>
6569 short q[4][3][2] = {
6570 { 1 },
6571 { 2, 3 },
6572 { 4, 5, 6 }
6573 };</pre>
6574 contains an incompletely but consistently bracketed initialization. It defines a three-dimensional array
6575 object: q[0][0][0] is 1, q[1][0][0] is 2, q[1][0][1] is 3, and 4, 5, and 6 initialize
6576 q[2][0][0], q[2][0][1], and q[2][1][0], respectively; all the rest are zero. The initializer for
6577 q[0][0] does not begin with a left brace, so up to six items from the current list may be used. There is
6578 only one, so the values for the remaining five elements are initialized with zero. Likewise, the initializers
6579 for q[1][0] and q[2][0] do not begin with a left brace, so each uses up to six items, initializing their
6580 respective two-dimensional subaggregates. If there had been more than six items in any of the lists, a
6581 diagnostic message would have been issued. The same initialization result could have been achieved by:
6582 <pre>
6583 short q[4][3][2] = {
6584 1, 0, 0, 0, 0, 0,
6585 2, 3, 0, 0, 0, 0,
6586 4, 5, 6
6587 };</pre>
6588 or by:
6589 <pre>
6590 short q[4][3][2] = {
6591 {
6592 { 1 },
6593 },
6594 {
6595 { 2, 3 },
6596 },
6597 {
6598 { 4, 5 },
6599 { 6 },
6600 }
6601 };</pre>
6602 in a fully bracketed form.
6603 <p><!--para 30 -->
6604 Note that the fully bracketed and minimally bracketed forms of initialization are, in general, less likely to
6605 cause confusion.
6607 <p><!--para 31 -->
6608 EXAMPLE 7 One form of initialization that completes array types involves typedef names. Given the
6609 declaration
6610 <pre>
6611 typedef int A[]; // OK - declared with block scope</pre>
6612 the declaration
6613 <pre>
6614 A a = { 1, 2 }, b = { 3, 4, 5 };</pre>
6615 is identical to
6616 <pre>
6617 int a[] = { 1, 2 }, b[] = { 3, 4, 5 };</pre>
6618 due to the rules for incomplete types.
6619 <!--page 142 -->
6620 <p><!--para 32 -->
6621 EXAMPLE 8 The declaration
6622 <pre>
6624 defines ''plain'' char array objects s and t whose elements are initialized with character string literals.
6625 This declaration is identical to
6626 <pre>
6627 char s[] = { 'a', 'b', 'c', '\0' },
6628 t[] = { 'a', 'b', 'c' };</pre>
6629 The contents of the arrays are modifiable. On the other hand, the declaration
6630 <pre>
6632 defines p with type ''pointer to char'' and initializes it to point to an object with type ''array of char''
6633 with length 4 whose elements are initialized with a character string literal. If an attempt is made to use p to
6634 modify the contents of the array, the behavior is undefined.
6636 <p><!--para 33 -->
6637 EXAMPLE 9 Arrays can be initialized to correspond to the elements of an enumeration by using
6638 designators:
6639 <pre>
6640 enum { member_one, member_two };
6641 const char *nm[] = {
6644 };</pre>
6646 <p><!--para 34 -->
6647 EXAMPLE 10 Structure members can be initialized to nonzero values without depending on their order:
6648 <pre>
6649 div_t answer = { .quot = 2, .rem = -1 };</pre>
6651 <p><!--para 35 -->
6652 EXAMPLE 11 Designators can be used to provide explicit initialization when unadorned initializer lists
6653 might be misunderstood:
6654 <pre>
6655 struct { int a[3], b; } w[] =
6656 { [0].a = {1}, [1].a[0] = 2 };</pre>
6658 <p><!--para 36 -->
6659 EXAMPLE 12 Space can be ''allocated'' from both ends of an array by using a single designator:
6660 <p><!--para 37 -->
6661 <pre>
6662 int a[MAX] = {
6663 1, 3, 5, 7, 9, [MAX-5] = 8, 6, 4, 2, 0
6664 };</pre>
6665 In the above, if MAX is greater than ten, there will be some zero-valued elements in the middle; if it is less
6666 than ten, some of the values provided by the first five initializers will be overridden by the second five.
6668 <p><!--para 38 -->
6669 EXAMPLE 13 Any member of a union can be initialized:
6670 <pre>
6671 union { /* ... */ } u = { .any_member = 42 };</pre>
6673 <p><b> Forward references</b>: common definitions <a href="#7.17"><stddef.h></a> (<a href="#7.17">7.17</a>).
6674 <!--page 143 -->
6676 <h6>footnotes</h6>
6677 <p><small><a name="note129" href="#note129">129)</a> If the initializer list for a subaggregate or contained union does not begin with a left brace, its
6678 subobjects are initialized as usual, but the subaggregate or contained union does not become the
6679 current object: current objects are associated only with brace-enclosed initializer lists.
6680 </small>
6681 <p><small><a name="note130" href="#note130">130)</a> After a union member is initialized, the next object is not the next member of the union; instead, it is
6682 the next subobject of an object containing the union.
6683 </small>
6684 <p><small><a name="note131" href="#note131">131)</a> Thus, a designator can only specify a strict subobject of the aggregate or union that is associated with
6685 the surrounding brace pair. Note, too, that each separate designator list is independent.
6686 </small>
6687 <p><small><a name="note132" href="#note132">132)</a> Any initializer for the subobject which is overridden and so not used to initialize that subobject might
6688 not be evaluated at all.
6689 </small>
6690 <p><small><a name="note133" href="#note133">133)</a> In particular, the evaluation order need not be the same as the order of subobject initialization.
6691 </small>
6694 <h6>Syntax</h6>
6695 <p><!--para 1 -->
6696 <pre>
6697 statement:
6698 labeled-statement
6699 compound-statement
6700 expression-statement
6701 selection-statement
6702 iteration-statement
6703 jump-statement</pre>
6704 <h6>Semantics</h6>
6705 <p><!--para 2 -->
6706 A statement specifies an action to be performed. Except as indicated, statements are
6707 executed in sequence.
6708 <p><!--para 3 -->
6709 A block allows a set of declarations and statements to be grouped into one syntactic unit.
6710 The initializers of objects that have automatic storage duration, and the variable length
6711 array declarators of ordinary identifiers with block scope, are evaluated and the values are
6712 stored in the objects (including storing an indeterminate value in objects without an
6713 initializer) each time the declaration is reached in the order of execution, as if it were a
6714 statement, and within each declaration in the order that declarators appear.
6715 <p><!--para 4 -->
6716 A full expression is an expression that is not part of another expression or of a declarator.
6717 Each of the following is a full expression: an initializer; the expression in an expression
6718 statement; the controlling expression of a selection statement (if or switch); the
6719 controlling expression of a while or do statement; each of the (optional) expressions of
6720 a for statement; the (optional) expression in a return statement. The end of a full
6721 expression is a sequence point.
6722 <p><b> Forward references</b>: expression and null statements (<a href="#6.8.3">6.8.3</a>), selection statements
6723 (<a href="#6.8.4">6.8.4</a>), iteration statements (<a href="#6.8.5">6.8.5</a>), the return statement (<a href="#6.8.6.4">6.8.6.4</a>).
6726 <h6>Syntax</h6>
6727 <p><!--para 1 -->
6728 <pre>
6729 labeled-statement:
6730 identifier : statement
6731 case constant-expression : statement
6732 default : statement</pre>
6733 <h6>Constraints</h6>
6734 <p><!--para 2 -->
6735 A case or default label shall appear only in a switch statement. Further
6736 constraints on such labels are discussed under the switch statement.
6737 <!--page 144 -->
6738 <p><!--para 3 -->
6739 Label names shall be unique within a function.
6740 <h6>Semantics</h6>
6741 <p><!--para 4 -->
6742 Any statement may be preceded by a prefix that declares an identifier as a label name.
6743 Labels in themselves do not alter the flow of control, which continues unimpeded across
6744 them.
6745 <p><b> Forward references</b>: the goto statement (<a href="#6.8.6.1">6.8.6.1</a>), the switch statement (<a href="#6.8.4.2">6.8.4.2</a>).
6748 <h6>Syntax</h6>
6749 <p><!--para 1 -->
6750 <pre>
6751 compound-statement:
6752 { block-item-listopt }
6753 block-item-list:
6754 block-item
6755 block-item-list block-item
6756 block-item:
6757 declaration
6758 statement</pre>
6759 <h6>Semantics</h6>
6760 <p><!--para 2 -->
6761 A compound statement is a block.
6764 <h6>Syntax</h6>
6765 <p><!--para 1 -->
6766 <pre>
6767 expression-statement:
6768 expressionopt ;</pre>
6769 <h6>Semantics</h6>
6770 <p><!--para 2 -->
6771 The expression in an expression statement is evaluated as a void expression for its side
6773 <p><!--para 3 -->
6774 A null statement (consisting of just a semicolon) performs no operations.
6775 <p><!--para 4 -->
6776 EXAMPLE 1 If a function call is evaluated as an expression statement for its side effects only, the
6777 discarding of its value may be made explicit by converting the expression to a void expression by means of
6778 a cast:
6779 <pre>
6780 int p(int);
6781 /* ... */
6782 (void)p(0);</pre>
6786 <!--page 145 -->
6787 <p><!--para 5 -->
6788 EXAMPLE 2 In the program fragment
6789 <pre>
6790 char *s;
6791 /* ... */
6792 while (*s++ != '\0')
6793 ;</pre>
6794 a null statement is used to supply an empty loop body to the iteration statement.
6796 <p><!--para 6 -->
6797 EXAMPLE 3 A null statement may also be used to carry a label just before the closing } of a compound
6798 statement.
6799 <pre>
6800 while (loop1) {
6801 /* ... */
6802 while (loop2) {
6803 /* ... */
6804 if (want_out)
6805 goto end_loop1;
6806 /* ... */
6807 }
6808 /* ... */
6809 end_loop1: ;
6810 }</pre>
6814 <h6>footnotes</h6>
6815 <p><small><a name="note134" href="#note134">134)</a> Such as assignments, and function calls which have side effects.
6816 </small>
6819 <h6>Syntax</h6>
6820 <p><!--para 1 -->
6821 <pre>
6822 selection-statement:
6823 if ( expression ) statement
6824 if ( expression ) statement else statement
6825 switch ( expression ) statement</pre>
6826 <h6>Semantics</h6>
6827 <p><!--para 2 -->
6828 A selection statement selects among a set of statements depending on the value of a
6829 controlling expression.
6830 <p><!--para 3 -->
6831 A selection statement is a block whose scope is a strict subset of the scope of its
6832 enclosing block. Each associated substatement is also a block whose scope is a strict
6833 subset of the scope of the selection statement.
6836 <h6>Constraints</h6>
6837 <p><!--para 1 -->
6838 The controlling expression of an if statement shall have scalar type.
6839 <h6>Semantics</h6>
6840 <p><!--para 2 -->
6841 In both forms, the first substatement is executed if the expression compares unequal to 0.
6842 In the else form, the second substatement is executed if the expression compares equal
6843 <!--page 146 -->
6844 to 0. If the first substatement is reached via a label, the second substatement is not
6845 executed.
6846 <p><!--para 3 -->
6847 An else is associated with the lexically nearest preceding if that is allowed by the
6848 syntax.
6851 <h6>Constraints</h6>
6852 <p><!--para 1 -->
6853 The controlling expression of a switch statement shall have integer type.
6854 <p><!--para 2 -->
6855 If a switch statement has an associated case or default label within the scope of an
6856 identifier with a variably modified type, the entire switch statement shall be within the
6858 <p><!--para 3 -->
6859 The expression of each case label shall be an integer constant expression and no two of
6860 the case constant expressions in the same switch statement shall have the same value
6861 after conversion. There may be at most one default label in a switch statement.
6862 (Any enclosed switch statement may have a default label or case constant
6863 expressions with values that duplicate case constant expressions in the enclosing
6864 switch statement.)
6865 <h6>Semantics</h6>
6866 <p><!--para 4 -->
6867 A switch statement causes control to jump to, into, or past the statement that is the
6868 switch body, depending on the value of a controlling expression, and on the presence of a
6869 default label and the values of any case labels on or in the switch body. A case or
6870 default label is accessible only within the closest enclosing switch statement.
6871 <p><!--para 5 -->
6872 The integer promotions are performed on the controlling expression. The constant
6873 expression in each case label is converted to the promoted type of the controlling
6874 expression. If a converted value matches that of the promoted controlling expression,
6875 control jumps to the statement following the matched case label. Otherwise, if there is
6876 a default label, control jumps to the labeled statement. If no converted case constant
6877 expression matches and there is no default label, no part of the switch body is
6878 executed.
6879 Implementation limits
6880 <p><!--para 6 -->
6881 As discussed in <a href="#5.2.4.1">5.2.4.1</a>, the implementation may limit the number of case values in a
6882 switch statement.
6887 <!--page 147 -->
6888 <p><!--para 7 -->
6889 EXAMPLE In the artificial program fragment
6890 <pre>
6891 switch (expr)
6892 {
6893 int i = 4;
6894 f(i);
6895 case 0:
6896 i = 17;
6897 /* falls through into default code */
6898 default:
6900 }</pre>
6901 the object whose identifier is i exists with automatic storage duration (within the block) but is never
6902 initialized, and thus if the controlling expression has a nonzero value, the call to the printf function will
6903 access an indeterminate value. Similarly, the call to the function f cannot be reached.
6906 <h6>footnotes</h6>
6907 <p><small><a name="note135" href="#note135">135)</a> That is, the declaration either precedes the switch statement, or it follows the last case or
6908 default label associated with the switch that is in the block containing the declaration.
6909 </small>
6912 <h6>Syntax</h6>
6913 <p><!--para 1 -->
6914 <pre>
6915 iteration-statement:
6916 while ( expression ) statement
6917 do statement while ( expression ) ;
6918 for ( expressionopt ; expressionopt ; expressionopt ) statement
6919 for ( declaration expressionopt ; expressionopt ) statement</pre>
6920 <h6>Constraints</h6>
6921 <p><!--para 2 -->
6922 The controlling expression of an iteration statement shall have scalar type.
6923 <p><!--para 3 -->
6924 The declaration part of a for statement shall only declare identifiers for objects having
6925 storage class auto or register.
6926 <h6>Semantics</h6>
6927 <p><!--para 4 -->
6928 An iteration statement causes a statement called the loop body to be executed repeatedly
6929 until the controlling expression compares equal to 0. The repetition occurs regardless of
6930 whether the loop body is entered from the iteration statement or by a jump.<sup><a href="#note136"><b>136)</b></a></sup>
6931 <p><!--para 5 -->
6932 An iteration statement is a block whose scope is a strict subset of the scope of its
6933 enclosing block. The loop body is also a block whose scope is a strict subset of the scope
6934 of the iteration statement.
6939 <!--page 148 -->
6941 <h6>footnotes</h6>
6942 <p><small><a name="note136" href="#note136">136)</a> Code jumped over is not executed. In particular, the controlling expression of a for or while
6943 statement is not evaluated before entering the loop body, nor is clause-1 of a for statement.
6944 </small>
6947 <p><!--para 1 -->
6948 The evaluation of the controlling expression takes place before each execution of the loop
6949 body.
6952 <p><!--para 1 -->
6953 The evaluation of the controlling expression takes place after each execution of the loop
6954 body.
6957 <p><!--para 1 -->
6958 The statement
6959 <pre>
6960 for ( clause-1 ; expression-2 ; expression-3 ) statement</pre>
6961 behaves as follows: The expression expression-2 is the controlling expression that is
6962 evaluated before each execution of the loop body. The expression expression-3 is
6963 evaluated as a void expression after each execution of the loop body. If clause-1 is a
6964 declaration, the scope of any identifiers it declares is the remainder of the declaration and
6965 the entire loop, including the other two expressions; it is reached in the order of execution
6966 before the first evaluation of the controlling expression. If clause-1 is an expression, it is
6967 evaluated as a void expression before the first evaluation of the controlling expression.<sup><a href="#note137"><b>137)</b></a></sup>
6968 <p><!--para 2 -->
6969 Both clause-1 and expression-3 can be omitted. An omitted expression-2 is replaced by a
6970 nonzero constant.
6972 <h6>footnotes</h6>
6973 <p><small><a name="note137" href="#note137">137)</a> Thus, clause-1 specifies initialization for the loop, possibly declaring one or more variables for use in
6974 the loop; the controlling expression, expression-2, specifies an evaluation made before each iteration,
6975 such that execution of the loop continues until the expression compares equal to 0; and expression-3
6976 specifies an operation (such as incrementing) that is performed after each iteration.
6977 </small>
6980 <h6>Syntax</h6>
6981 <p><!--para 1 -->
6982 <pre>
6983 jump-statement:
6984 goto identifier ;
6985 continue ;
6986 break ;
6987 return expressionopt ;</pre>
6988 <h6>Semantics</h6>
6989 <p><!--para 2 -->
6990 A jump statement causes an unconditional jump to another place.
6995 <!--page 149 -->
6998 <h6>Constraints</h6>
6999 <p><!--para 1 -->
7000 The identifier in a goto statement shall name a label located somewhere in the enclosing
7001 function. A goto statement shall not jump from outside the scope of an identifier having
7002 a variably modified type to inside the scope of that identifier.
7003 <h6>Semantics</h6>
7004 <p><!--para 2 -->
7005 A goto statement causes an unconditional jump to the statement prefixed by the named
7006 label in the enclosing function.
7007 <p><!--para 3 -->
7008 EXAMPLE 1 It is sometimes convenient to jump into the middle of a complicated set of statements. The
7009 following outline presents one possible approach to a problem based on these three assumptions:
7010 <ol>
7011 <li> The general initialization code accesses objects only visible to the current function.
7012 <li> The general initialization code is too large to warrant duplication.
7013 <li> The code to determine the next operation is at the head of the loop. (To allow it to be reached by
7014 continue statements, for example.)
7015 /* ... */
7016 goto first_time;
7017 for (;;) {
7018 <pre>
7019 // determine next operation
7020 /* ... */
7021 if (need to reinitialize) {
7022 // reinitialize-only code
7023 /* ... */
7024 first_time:
7025 // general initialization code
7026 /* ... */
7027 continue;
7028 }
7029 // handle other operations
7030 /* ... */</pre>
7031 }
7032 <!--page 150 -->
7033 </ol>
7034 <p><!--para 4 -->
7035 EXAMPLE 2 A goto statement is not allowed to jump past any declarations of objects with variably
7036 modified types. A jump within the scope, however, is permitted.
7037 <pre>
7038 goto lab3; // invalid: going INTO scope of VLA.
7039 {
7040 double a[n];
7042 lab3:
7044 goto lab4; // valid: going WITHIN scope of VLA.
7046 lab4:
7048 }
7049 goto lab4; // invalid: going INTO scope of VLA.</pre>
7053 <h6>Constraints</h6>
7054 <p><!--para 1 -->
7055 A continue statement shall appear only in or as a loop body.
7056 <h6>Semantics</h6>
7057 <p><!--para 2 -->
7058 A continue statement causes a jump to the loop-continuation portion of the smallest
7059 enclosing iteration statement; that is, to the end of the loop body. More precisely, in each
7060 of the statements
7061 while (/* ... */) { do { for (/* ... */) {
7062 <pre>
7063 /* ... */ /* ... */ /* ... */
7064 continue; continue; continue;
7065 /* ... */ /* ... */ /* ... */</pre>
7066 contin: ; contin: ; contin: ;
7067 } } while (/* ... */); }
7068 unless the continue statement shown is in an enclosed iteration statement (in which
7069 case it is interpreted within that statement), it is equivalent to goto contin;.<sup><a href="#note138"><b>138)</b></a></sup>
7071 <h6>footnotes</h6>
7072 <p><small><a name="note138" href="#note138">138)</a> Following the contin: label is a null statement.
7073 </small>
7076 <h6>Constraints</h6>
7077 <p><!--para 1 -->
7078 A break statement shall appear only in or as a switch body or loop body.
7079 <h6>Semantics</h6>
7080 <p><!--para 2 -->
7081 A break statement terminates execution of the smallest enclosing switch or iteration
7082 statement.
7086 <!--page 151 -->
7089 <h6>Constraints</h6>
7090 <p><!--para 1 -->
7091 A return statement with an expression shall not appear in a function whose return type
7092 is void. A return statement without an expression shall only appear in a function
7093 whose return type is void.
7094 <h6>Semantics</h6>
7095 <p><!--para 2 -->
7096 A return statement terminates execution of the current function and returns control to
7097 its caller. A function may have any number of return statements.
7098 <p><!--para 3 -->
7099 If a return statement with an expression is executed, the value of the expression is
7100 returned to the caller as the value of the function call expression. If the expression has a
7101 type different from the return type of the function in which it appears, the value is
7102 converted as if by assignment to an object having the return type of the function.<sup><a href="#note139"><b>139)</b></a></sup>
7103 <p><!--para 4 -->
7104 EXAMPLE In:
7105 <pre>
7106 struct s { double i; } f(void);
7107 union {
7108 struct {
7109 int f1;
7110 struct s f2;
7111 } u1;
7112 struct {
7113 struct s f3;
7114 int f4;
7115 } u2;
7116 } g;
7117 struct s f(void)
7118 {
7119 return g.u1.f2;
7120 }
7121 /* ... */
7122 g.u2.f3 = f();</pre>
7123 there is no undefined behavior, although there would be if the assignment were done directly (without using
7124 a function call to fetch the value).
7129 <!--page 152 -->
7131 <h6>footnotes</h6>
7132 <p><small><a name="note139" href="#note139">139)</a> The return statement is not an assignment. The overlap restriction of subclause <a href="#6.5.16.1">6.5.16.1</a> does not
7133 apply to the case of function return. The representation of floating-point values may have wider range
7134 or precision and is determined by FLT_EVAL_METHOD. A cast may be used to remove this extra
7135 range and precision.
7136 </small>
7139 <h6>Syntax</h6>
7140 <p><!--para 1 -->
7141 <pre>
7142 translation-unit:
7143 external-declaration
7144 translation-unit external-declaration
7145 external-declaration:
7146 function-definition
7147 declaration</pre>
7148 <h6>Constraints</h6>
7149 <p><!--para 2 -->
7150 The storage-class specifiers auto and register shall not appear in the declaration
7151 specifiers in an external declaration.
7152 <p><!--para 3 -->
7153 There shall be no more than one external definition for each identifier declared with
7154 internal linkage in a translation unit. Moreover, if an identifier declared with internal
7155 linkage is used in an expression (other than as a part of the operand of a sizeof
7156 operator whose result is an integer constant), there shall be exactly one external definition
7157 for the identifier in the translation unit.
7158 <h6>Semantics</h6>
7159 <p><!--para 4 -->
7160 As discussed in <a href="#5.1.1.1">5.1.1.1</a>, the unit of program text after preprocessing is a translation unit,
7161 which consists of a sequence of external declarations. These are described as ''external''
7162 because they appear outside any function (and hence have file scope). As discussed in
7163 <a href="#6.7">6.7</a>, a declaration that also causes storage to be reserved for an object or a function named
7164 by the identifier is a definition.
7165 <p><!--para 5 -->
7166 An external definition is an external declaration that is also a definition of a function
7167 (other than an inline definition) or an object. If an identifier declared with external
7168 linkage is used in an expression (other than as part of the operand of a sizeof operator
7169 whose result is an integer constant), somewhere in the entire program there shall be
7170 exactly one external definition for the identifier; otherwise, there shall be no more than
7176 <!--page 153 -->
7178 <h6>footnotes</h6>
7179 <p><small><a name="note140" href="#note140">140)</a> Thus, if an identifier declared with external linkage is not used in an expression, there need be no
7180 external definition for it.
7181 </small>
7184 <h6>Syntax</h6>
7185 <p><!--para 1 -->
7186 <pre>
7187 function-definition:
7188 declaration-specifiers declarator declaration-listopt compound-statement
7189 declaration-list:
7190 declaration
7191 declaration-list declaration</pre>
7192 <h6>Constraints</h6>
7193 <p><!--para 2 -->
7194 The identifier declared in a function definition (which is the name of the function) shall
7195 have a function type, as specified by the declarator portion of the function definition.<sup><a href="#note141"><b>141)</b></a></sup>
7196 <p><!--para 3 -->
7197 The return type of a function shall be void or an object type other than array type.
7198 <p><!--para 4 -->
7199 The storage-class specifier, if any, in the declaration specifiers shall be either extern or
7200 static.
7201 <p><!--para 5 -->
7202 If the declarator includes a parameter type list, the declaration of each parameter shall
7203 include an identifier, except for the special case of a parameter list consisting of a single
7204 parameter of type void, in which case there shall not be an identifier. No declaration list
7205 shall follow.
7206 <p><!--para 6 -->
7207 If the declarator includes an identifier list, each declaration in the declaration list shall
7208 have at least one declarator, those declarators shall declare only identifiers from the
7209 identifier list, and every identifier in the identifier list shall be declared. An identifier
7210 declared as a typedef name shall not be redeclared as a parameter. The declarations in the
7211 declaration list shall contain no storage-class specifier other than register and no
7212 initializations.
7217 <!--page 154 -->
7218 <h6>Semantics</h6>
7219 <p><!--para 7 -->
7220 The declarator in a function definition specifies the name of the function being defined
7221 and the identifiers of its parameters. If the declarator includes a parameter type list, the
7222 list also specifies the types of all the parameters; such a declarator also serves as a
7223 function prototype for later calls to the same function in the same translation unit. If the
7224 declarator includes an identifier list,<sup><a href="#note142"><b>142)</b></a></sup> the types of the parameters shall be declared in a
7225 following declaration list. In either case, the type of each parameter is adjusted as
7226 described in <a href="#6.7.5.3">6.7.5.3</a> for a parameter type list; the resulting type shall be an object type.
7227 <p><!--para 8 -->
7228 If a function that accepts a variable number of arguments is defined without a parameter
7229 type list that ends with the ellipsis notation, the behavior is undefined.
7230 <p><!--para 9 -->
7231 Each parameter has automatic storage duration. Its identifier is an lvalue, which is in
7232 effect declared at the head of the compound statement that constitutes the function body
7233 (and therefore cannot be redeclared in the function body except in an enclosed block).
7234 The layout of the storage for parameters is unspecified.
7235 <p><!--para 10 -->
7236 On entry to the function, the size expressions of each variably modified parameter are
7237 evaluated and the value of each argument expression is converted to the type of the
7238 corresponding parameter as if by assignment. (Array expressions and function
7239 designators as arguments were converted to pointers before the call.)
7240 <p><!--para 11 -->
7241 After all parameters have been assigned, the compound statement that constitutes the
7242 body of the function definition is executed.
7243 <p><!--para 12 -->
7244 If the } that terminates a function is reached, and the value of the function call is used by
7245 the caller, the behavior is undefined.
7246 <p><!--para 13 -->
7247 EXAMPLE 1 In the following:
7248 <pre>
7249 extern int max(int a, int b)
7250 {
7251 return a > b ? a : b;
7252 }</pre>
7253 extern is the storage-class specifier and int is the type specifier; max(int a, int b) is the
7254 function declarator; and
7255 <pre>
7256 { return a > b ? a : b; }</pre>
7257 is the function body. The following similar definition uses the identifier-list form for the parameter
7258 declarations:
7263 <!--page 155 -->
7264 <pre>
7265 extern int max(a, b)
7266 int a, b;
7267 {
7268 return a > b ? a : b;
7269 }</pre>
7270 Here int a, b; is the declaration list for the parameters. The difference between these two definitions is
7271 that the first form acts as a prototype declaration that forces conversion of the arguments of subsequent calls
7272 to the function, whereas the second form does not.
7274 <p><!--para 14 -->
7275 EXAMPLE 2 To pass one function to another, one might say
7276 <pre>
7277 int f(void);
7278 /* ... */
7279 g(f);</pre>
7280 Then the definition of g might read
7281 <pre>
7282 void g(int (*funcp)(void))
7283 {
7284 /* ... */
7285 (*funcp)(); /* or funcp(); ... */
7286 }</pre>
7287 or, equivalently,
7288 <pre>
7289 void g(int func(void))
7290 {
7291 /* ... */
7292 func(); /* or (*func)(); ... */
7293 }</pre>
7296 <h6>footnotes</h6>
7297 <p><small><a name="note141" href="#note141">141)</a> The intent is that the type category in a function definition cannot be inherited from a typedef:
7299 <pre>
7300 typedef int F(void); // type F is ''function with no parameters
7301 // returning int''
7302 F f, g; // f and g both have type compatible with F
7303 F f { /* ... */ } // WRONG: syntax/constraint error
7304 F g() { /* ... */ } // WRONG: declares that g returns a function
7305 int f(void) { /* ... */ } // RIGHT: f has type compatible with F
7306 int g() { /* ... */ } // RIGHT: g has type compatible with F
7307 F *e(void) { /* ... */ } // e returns a pointer to a function
7308 F *((e))(void) { /* ... */ } // same: parentheses irrelevant
7309 int (*fp)(void); // fp points to a function that has type F
7310 F *Fp; // Fp points to a function that has type F</pre>
7311 </small>
7312 <p><small><a name="note142" href="#note142">142)</a> See ''future language directions'' (<a href="#6.11.7">6.11.7</a>).
7313 </small>
7316 <h6>Semantics</h6>
7317 <p><!--para 1 -->
7318 If the declaration of an identifier for an object has file scope and an initializer, the
7319 declaration is an external definition for the identifier.
7320 <p><!--para 2 -->
7321 A declaration of an identifier for an object that has file scope without an initializer, and
7322 without a storage-class specifier or with the storage-class specifier static, constitutes a
7323 tentative definition. If a translation unit contains one or more tentative definitions for an
7324 identifier, and the translation unit contains no external definition for that identifier, then
7325 the behavior is exactly as if the translation unit contains a file scope declaration of that
7326 identifier, with the composite type as of the end of the translation unit, with an initializer
7327 equal to 0.
7328 <p><!--para 3 -->
7329 If the declaration of an identifier for an object is a tentative definition and has internal
7330 linkage, the declared type shall not be an incomplete type.
7331 <!--page 156 -->
7332 <p><!--para 4 -->
7333 EXAMPLE 1
7334 <pre>
7335 int i1 = 1; // definition, external linkage
7336 static int i2 = 2; // definition, internal linkage
7337 extern int i3 = 3; // definition, external linkage
7338 int i4; // tentative definition, external linkage
7339 static int i5; // tentative definition, internal linkage
7340 int i1; // valid tentative definition, refers to previous
7342 int i3; // valid tentative definition, refers to previous
7343 int i4; // valid tentative definition, refers to previous
7345 extern int i1; // refers to previous, whose linkage is external
7346 extern int i2; // refers to previous, whose linkage is internal
7347 extern int i3; // refers to previous, whose linkage is external
7348 extern int i4; // refers to previous, whose linkage is external
7349 extern int i5; // refers to previous, whose linkage is internal</pre>
7351 <p><!--para 5 -->
7352 EXAMPLE 2 If at the end of the translation unit containing
7353 <pre>
7354 int i[];</pre>
7355 the array i still has incomplete type, the implicit initializer causes it to have one element, which is set to
7356 zero on program startup.
7357 <!--page 157 -->
7360 <h6>Syntax</h6>
7361 <p><!--para 1 -->
7362 <!--page 158 -->
7363 <pre>
7364 preprocessing-file:
7365 groupopt
7366 group:
7367 group-part
7368 group group-part
7369 group-part:
7370 if-section
7371 control-line
7372 text-line
7373 # non-directive
7374 if-section:
7375 if-group elif-groupsopt else-groupopt endif-line
7376 if-group:
7377 # if constant-expression new-line groupopt
7378 # ifdef identifier new-line groupopt
7379 # ifndef identifier new-line groupopt
7380 elif-groups:
7381 elif-group
7382 elif-groups elif-group
7383 elif-group:
7384 # elif constant-expression new-line groupopt
7385 else-group:
7386 # else new-line groupopt
7387 endif-line:
7388 # endif new-line
7389 control-line:
7390 # include pp-tokens new-line
7391 # define identifier replacement-list new-line
7392 # define identifier lparen identifier-listopt )
7393 replacement-list new-line
7394 # define identifier lparen ... ) replacement-list new-line
7395 # define identifier lparen identifier-list , ... )
7396 replacement-list new-line
7397 # undef identifier new-line
7398 # line pp-tokens new-line
7399 # error pp-tokensopt new-line
7400 # pragma pp-tokensopt new-line
7401 # new-line
7402 text-line:
7403 pp-tokensopt new-line
7404 non-directive:
7405 pp-tokens new-line
7406 lparen:
7407 a ( character not immediately preceded by white-space
7408 replacement-list:
7409 pp-tokensopt
7410 pp-tokens:
7411 preprocessing-token
7412 pp-tokens preprocessing-token
7413 new-line:
7414 the new-line character</pre>
7415 <h6>Description</h6>
7416 <p><!--para 2 -->
7417 A preprocessing directive consists of a sequence of preprocessing tokens that satisfies the
7418 following constraints: The first token in the sequence is a # preprocessing token that (at
7419 the start of translation phase 4) is either the first character in the source file (optionally
7420 after white space containing no new-line characters) or that follows white space
7421 containing at least one new-line character. The last token in the sequence is the first new-
7422 line character that follows the first token in the sequence.<sup><a href="#note143"><b>143)</b></a></sup> A new-line character ends
7423 the preprocessing directive even if it occurs within what would otherwise be an
7425 <!--page 159 -->
7426 invocation of a function-like macro.
7427 <p><!--para 3 -->
7428 A text line shall not begin with a # preprocessing token. A non-directive shall not begin
7429 with any of the directive names appearing in the syntax.
7430 <p><!--para 4 -->
7431 When in a group that is skipped (<a href="#6.10.1">6.10.1</a>), the directive syntax is relaxed to allow any
7432 sequence of preprocessing tokens to occur between the directive name and the following
7433 new-line character.
7434 <h6>Constraints</h6>
7435 <p><!--para 5 -->
7436 The only white-space characters that shall appear between preprocessing tokens within a
7437 preprocessing directive (from just after the introducing # preprocessing token through
7438 just before the terminating new-line character) are space and horizontal-tab (including
7439 spaces that have replaced comments or possibly other white-space characters in
7440 translation phase 3).
7441 <h6>Semantics</h6>
7442 <p><!--para 6 -->
7443 The implementation can process and skip sections of source files conditionally, include
7444 other source files, and replace macros. These capabilities are called preprocessing,
7445 because conceptually they occur before translation of the resulting translation unit.
7446 <p><!--para 7 -->
7447 The preprocessing tokens within a preprocessing directive are not subject to macro
7448 expansion unless otherwise stated.
7449 <p><!--para 8 -->
7450 EXAMPLE In:
7451 <pre>
7452 #define EMPTY
7453 EMPTY # include <file.h></pre>
7454 the sequence of preprocessing tokens on the second line is not a preprocessing directive, because it does not
7455 begin with a # at the start of translation phase 4, even though it will do so after the macro EMPTY has been
7456 replaced.
7459 <h6>footnotes</h6>
7460 <p><small><a name="note143" href="#note143">143)</a> Thus, preprocessing directives are commonly called ''lines''. These ''lines'' have no other syntactic
7461 significance, as all white space is equivalent except in certain situations during preprocessing (see the
7462 # character string literal creation operator in <a href="#6.10.3.2">6.10.3.2</a>, for example).
7463 </small>
7466 <h6>Constraints</h6>
7467 <p><!--para 1 -->
7468 The expression that controls conditional inclusion shall be an integer constant expression
7469 except that: it shall not contain a cast; identifiers (including those lexically identical to
7470 keywords) are interpreted as described below;<sup><a href="#note144"><b>144)</b></a></sup> and it may contain unary operator
7471 expressions of the form
7476 <!--page 160 -->
7477 <pre>
7478 defined identifier</pre>
7479 or
7480 <pre>
7481 defined ( identifier )</pre>
7482 which evaluate to 1 if the identifier is currently defined as a macro name (that is, if it is
7483 predefined or if it has been the subject of a #define preprocessing directive without an
7484 intervening #undef directive with the same subject identifier), 0 if it is not.
7485 <p><!--para 2 -->
7486 Each preprocessing token that remains (in the list of preprocessing tokens that will
7487 become the controlling expression) after all macro replacements have occurred shall be in
7489 <h6>Semantics</h6>
7490 <p><!--para 3 -->
7491 Preprocessing directives of the forms
7492 <pre>
7493 # if constant-expression new-line groupopt
7494 # elif constant-expression new-line groupopt</pre>
7495 check whether the controlling constant expression evaluates to nonzero.
7496 <p><!--para 4 -->
7497 Prior to evaluation, macro invocations in the list of preprocessing tokens that will become
7498 the controlling constant expression are replaced (except for those macro names modified
7499 by the defined unary operator), just as in normal text. If the token defined is
7500 generated as a result of this replacement process or use of the defined unary operator
7501 does not match one of the two specified forms prior to macro replacement, the behavior is
7502 undefined. After all replacements due to macro expansion and the defined unary
7503 operator have been performed, all remaining identifiers (including those lexically
7504 identical to keywords) are replaced with the pp-number 0, and then each preprocessing
7505 token is converted into a token. The resulting tokens compose the controlling constant
7506 expression which is evaluated according to the rules of <a href="#6.6">6.6</a>. For the purposes of this
7507 token conversion and evaluation, all signed integer types and all unsigned integer types
7508 act as if they have the same representation as, respectively, the types intmax_t and
7509 uintmax_t defined in the header <a href="#7.18"><stdint.h></a>.<sup><a href="#note145"><b>145)</b></a></sup> This includes interpreting
7510 character constants, which may involve converting escape sequences into execution
7511 character set members. Whether the numeric value for these character constants matches
7512 the value obtained when an identical character constant occurs in an expression (other
7513 than within a #if or #elif directive) is implementation-defined.<sup><a href="#note146"><b>146)</b></a></sup> Also, whether a
7514 single-character character constant may have a negative value is implementation-defined.
7515 <p><!--para 5 -->
7516 Preprocessing directives of the forms
7520 <!--page 161 -->
7521 <pre>
7522 # ifdef identifier new-line groupopt
7523 # ifndef identifier new-line groupopt</pre>
7524 check whether the identifier is or is not currently defined as a macro name. Their
7525 conditions are equivalent to #if defined identifier and #if !defined identifier
7526 respectively.
7527 <p><!--para 6 -->
7528 Each directive's condition is checked in order. If it evaluates to false (zero), the group
7529 that it controls is skipped: directives are processed only through the name that determines
7530 the directive in order to keep track of the level of nested conditionals; the rest of the
7531 directives' preprocessing tokens are ignored, as are the other preprocessing tokens in the
7532 group. Only the first group whose control condition evaluates to true (nonzero) is
7533 processed. If none of the conditions evaluates to true, and there is a #else directive, the
7534 group controlled by the #else is processed; lacking a #else directive, all the groups
7536 <p><b> Forward references</b>: macro replacement (<a href="#6.10.3">6.10.3</a>), source file inclusion (<a href="#6.10.2">6.10.2</a>), largest
7539 <h6>footnotes</h6>
7540 <p><small><a name="note144" href="#note144">144)</a> Because the controlling constant expression is evaluated during translation phase 4, all identifiers
7541 either are or are not macro names -- there simply are no keywords, enumeration constants, etc.
7542 </small>
7543 <p><small><a name="note145" href="#note145">145)</a> Thus, on an implementation where INT_MAX is 0x7FFF and UINT_MAX is 0xFFFF, the constant
7544 0x8000 is signed and positive within a #if expression even though it would be unsigned in
7545 translation phase 7.
7546 </small>
7547 <p><small><a name="note146" href="#note146">146)</a> Thus, the constant expression in the following #if directive and if statement is not guaranteed to
7548 evaluate to the same value in these two contexts.
7549 #if 'z' - 'a' == 25
7550 if ('z' - 'a' == 25)
7552 </small>
7553 <p><small><a name="note147" href="#note147">147)</a> As indicated by the syntax, a preprocessing token shall not follow a #else or #endif directive
7554 before the terminating new-line character. However, comments may appear anywhere in a source file,
7555 including within a preprocessing directive.
7556 </small>
7559 <h6>Constraints</h6>
7560 <p><!--para 1 -->
7561 A #include directive shall identify a header or source file that can be processed by the
7562 implementation.
7563 <h6>Semantics</h6>
7564 <p><!--para 2 -->
7565 A preprocessing directive of the form
7566 <pre>
7567 # include <h-char-sequence> new-line</pre>
7568 searches a sequence of implementation-defined places for a header identified uniquely by
7569 the specified sequence between the < and > delimiters, and causes the replacement of that
7570 directive by the entire contents of the header. How the places are specified or the header
7571 identified is implementation-defined.
7572 <p><!--para 3 -->
7573 A preprocessing directive of the form
7577 <!--page 162 -->
7578 <pre>
7580 causes the replacement of that directive by the entire contents of the source file identified
7581 by the specified sequence between the " delimiters. The named source file is searched
7582 for in an implementation-defined manner. If this search is not supported, or if the search
7583 fails, the directive is reprocessed as if it read
7584 <pre>
7586 with the identical contained sequence (including > characters, if any) from the original
7587 directive.
7589 A preprocessing directive of the form
7590 <pre>
7591 # include pp-tokens new-line</pre>
7592 (that does not match one of the two previous forms) is permitted. The preprocessing
7593 tokens after include in the directive are processed just as in normal text. (Each
7594 identifier currently defined as a macro name is replaced by its replacement list of
7595 preprocessing tokens.) The directive resulting after all replacements shall match one of
7596 the two previous forms.<sup><a href="#note148"><b>148)</b></a></sup> The method by which a sequence of preprocessing tokens
7597 between a < and a > preprocessing token pair or a pair of " characters is combined into a
7598 single header name preprocessing token is implementation-defined.
7599 <p><!--para 5 -->
7600 The implementation shall provide unique mappings for sequences consisting of one or
7601 more nondigits or digits (<a href="#6.4.2.1">6.4.2.1</a>) followed by a period (.) and a single nondigit. The
7602 first character shall not be a digit. The implementation may ignore distinctions of
7603 alphabetical case and restrict the mapping to eight significant characters before the
7604 period.
7605 <p><!--para 6 -->
7606 A #include preprocessing directive may appear in a source file that has been read
7607 because of a #include directive in another file, up to an implementation-defined
7609 <p><!--para 7 -->
7610 EXAMPLE 1 The most common uses of #include preprocessing directives are as in the following:
7611 <pre>
7615 <p><!--para 8 -->
7616 EXAMPLE 2 This illustrates macro-replaced #include directives:
7621 <!--page 163 -->
7622 <pre>
7623 #if VERSION == 1
7625 #elif VERSION == 2
7627 #else
7629 #endif
7630 #include INCFILE</pre>
7634 <h6>footnotes</h6>
7635 <p><small><a name="note148" href="#note148">148)</a> Note that adjacent string literals are not concatenated into a single string literal (see the translation
7636 phases in <a href="#5.1.1.2">5.1.1.2</a>); thus, an expansion that results in two string literals is an invalid directive.
7637 </small>
7640 <h6>Constraints</h6>
7641 <p><!--para 1 -->
7642 Two replacement lists are identical if and only if the preprocessing tokens in both have
7643 the same number, ordering, spelling, and white-space separation, where all white-space
7644 separations are considered identical.
7645 <p><!--para 2 -->
7646 An identifier currently defined as an object-like macro shall not be redefined by another
7647 #define preprocessing directive unless the second definition is an object-like macro
7648 definition and the two replacement lists are identical. Likewise, an identifier currently
7649 defined as a function-like macro shall not be redefined by another #define
7650 preprocessing directive unless the second definition is a function-like macro definition
7651 that has the same number and spelling of parameters, and the two replacement lists are
7652 identical.
7653 <p><!--para 3 -->
7654 There shall be white-space between the identifier and the replacement list in the definition
7655 of an object-like macro.
7656 <p><!--para 4 -->
7657 If the identifier-list in the macro definition does not end with an ellipsis, the number of
7658 arguments (including those arguments consisting of no preprocessing tokens) in an
7659 invocation of a function-like macro shall equal the number of parameters in the macro
7660 definition. Otherwise, there shall be more arguments in the invocation than there are
7661 parameters in the macro definition (excluding the ...). There shall exist a )
7662 preprocessing token that terminates the invocation.
7663 <p><!--para 5 -->
7664 The identifier __VA_ARGS__ shall occur only in the replacement-list of a function-like
7665 macro that uses the ellipsis notation in the parameters.
7666 <p><!--para 6 -->
7667 A parameter identifier in a function-like macro shall be uniquely declared within its
7668 scope.
7669 <h6>Semantics</h6>
7670 <p><!--para 7 -->
7671 The identifier immediately following the define is called the macro name. There is one
7672 name space for macro names. Any white-space characters preceding or following the
7673 replacement list of preprocessing tokens are not considered part of the replacement list
7674 for either form of macro.
7675 <!--page 164 -->
7676 <p><!--para 8 -->
7677 If a # preprocessing token, followed by an identifier, occurs lexically at the point at which
7678 a preprocessing directive could begin, the identifier is not subject to macro replacement.
7679 <p><!--para 9 -->
7680 A preprocessing directive of the form
7681 <pre>
7682 # define identifier replacement-list new-line</pre>
7683 defines an object-like macro that causes each subsequent instance of the macro name<sup><a href="#note149"><b>149)</b></a></sup>
7684 to be replaced by the replacement list of preprocessing tokens that constitute the
7685 remainder of the directive. The replacement list is then rescanned for more macro names
7686 as specified below.
7687 <p><!--para 10 -->
7688 A preprocessing directive of the form
7689 <pre>
7690 # define identifier lparen identifier-listopt ) replacement-list new-line
7691 # define identifier lparen ... ) replacement-list new-line
7692 # define identifier lparen identifier-list , ... ) replacement-list new-line</pre>
7693 defines a function-like macro with parameters, whose use is similar syntactically to a
7694 function call. The parameters are specified by the optional list of identifiers, whose scope
7695 extends from their declaration in the identifier list until the new-line character that
7696 terminates the #define preprocessing directive. Each subsequent instance of the
7697 function-like macro name followed by a ( as the next preprocessing token introduces the
7698 sequence of preprocessing tokens that is replaced by the replacement list in the definition
7699 (an invocation of the macro). The replaced sequence of preprocessing tokens is
7700 terminated by the matching ) preprocessing token, skipping intervening matched pairs of
7701 left and right parenthesis preprocessing tokens. Within the sequence of preprocessing
7702 tokens making up an invocation of a function-like macro, new-line is considered a normal
7703 white-space character.
7704 <p><!--para 11 -->
7705 The sequence of preprocessing tokens bounded by the outside-most matching parentheses
7706 forms the list of arguments for the function-like macro. The individual arguments within
7707 the list are separated by comma preprocessing tokens, but comma preprocessing tokens
7708 between matching inner parentheses do not separate arguments. If there are sequences of
7709 preprocessing tokens within the list of arguments that would otherwise act as
7710 preprocessing directives,<sup><a href="#note150"><b>150)</b></a></sup> the behavior is undefined.
7711 <p><!--para 12 -->
7712 If there is a ... in the identifier-list in the macro definition, then the trailing arguments,
7713 including any separating comma preprocessing tokens, are merged to form a single item:
7714 the variable arguments. The number of arguments so combined is such that, following
7717 <!--page 165 -->
7718 merger, the number of arguments is one more than the number of parameters in the macro
7719 definition (excluding the ...).
7721 <h6>footnotes</h6>
7722 <p><small><a name="note149" href="#note149">149)</a> Since, by macro-replacement time, all character constants and string literals are preprocessing tokens,
7723 not sequences possibly containing identifier-like subsequences (see <a href="#5.1.1.2">5.1.1.2</a>, translation phases), they
7724 are never scanned for macro names or parameters.
7725 </small>
7726 <p><small><a name="note150" href="#note150">150)</a> Despite the name, a non-directive is a preprocessing directive.
7727 </small>
7730 <p><!--para 1 -->
7731 After the arguments for the invocation of a function-like macro have been identified,
7732 argument substitution takes place. A parameter in the replacement list, unless preceded
7733 by a # or ## preprocessing token or followed by a ## preprocessing token (see below), is
7734 replaced by the corresponding argument after all macros contained therein have been
7735 expanded. Before being substituted, each argument's preprocessing tokens are
7736 completely macro replaced as if they formed the rest of the preprocessing file; no other
7737 preprocessing tokens are available.
7738 <p><!--para 2 -->
7739 An identifier __VA_ARGS__ that occurs in the replacement list shall be treated as if it
7740 were a parameter, and the variable arguments shall form the preprocessing tokens used to
7741 replace it.
7744 <h6>Constraints</h6>
7745 <p><!--para 1 -->
7746 Each # preprocessing token in the replacement list for a function-like macro shall be
7747 followed by a parameter as the next preprocessing token in the replacement list.
7748 <h6>Semantics</h6>
7749 <p><!--para 2 -->
7750 If, in the replacement list, a parameter is immediately preceded by a # preprocessing
7751 token, both are replaced by a single character string literal preprocessing token that
7752 contains the spelling of the preprocessing token sequence for the corresponding
7753 argument. Each occurrence of white space between the argument's preprocessing tokens
7754 becomes a single space character in the character string literal. White space before the
7755 first preprocessing token and after the last preprocessing token composing the argument
7756 is deleted. Otherwise, the original spelling of each preprocessing token in the argument
7757 is retained in the character string literal, except for special handling for producing the
7758 spelling of string literals and character constants: a \ character is inserted before each "
7759 and \ character of a character constant or string literal (including the delimiting "
7760 characters), except that it is implementation-defined whether a \ character is inserted
7761 before the \ character beginning a universal character name. If the replacement that
7762 results is not a valid character string literal, the behavior is undefined. The character
7764 ## operators is unspecified.
7765 <!--page 166 -->
7768 <h6>Constraints</h6>
7769 <p><!--para 1 -->
7770 A ## preprocessing token shall not occur at the beginning or at the end of a replacement
7771 list for either form of macro definition.
7772 <h6>Semantics</h6>
7773 <p><!--para 2 -->
7774 If, in the replacement list of a function-like macro, a parameter is immediately preceded
7775 or followed by a ## preprocessing token, the parameter is replaced by the corresponding
7776 argument's preprocessing token sequence; however, if an argument consists of no
7777 preprocessing tokens, the parameter is replaced by a placemarker preprocessing token
7779 <p><!--para 3 -->
7780 For both object-like and function-like macro invocations, before the replacement list is
7781 reexamined for more macro names to replace, each instance of a ## preprocessing token
7782 in the replacement list (not from an argument) is deleted and the preceding preprocessing
7783 token is concatenated with the following preprocessing token. Placemarker
7784 preprocessing tokens are handled specially: concatenation of two placemarkers results in
7785 a single placemarker preprocessing token, and concatenation of a placemarker with a
7786 non-placemarker preprocessing token results in the non-placemarker preprocessing token.
7787 If the result is not a valid preprocessing token, the behavior is undefined. The resulting
7788 token is available for further macro replacement. The order of evaluation of ## operators
7789 is unspecified.
7790 <p><!--para 4 -->
7791 EXAMPLE In the following fragment:
7792 <pre>
7793 #define hash_hash # ## #
7794 #define mkstr(a) # a
7795 #define in_between(a) mkstr(a)
7796 #define join(c, d) in_between(c hash_hash d)
7797 char p[] = join(x, y); // equivalent to
7799 The expansion produces, at various stages:
7800 <pre>
7801 join(x, y)
7802 in_between(x hash_hash y)
7803 in_between(x ## y)
7804 mkstr(x ## y)
7806 In other words, expanding hash_hash produces a new token, consisting of two adjacent sharp signs, but
7807 this new token is not the ## operator.
7810 <!--page 167 -->
7812 <h6>footnotes</h6>
7813 <p><small><a name="note151" href="#note151">151)</a> Placemarker preprocessing tokens do not appear in the syntax because they are temporary entities that
7814 exist only within translation phase 4.
7815 </small>
7818 <p><!--para 1 -->
7819 After all parameters in the replacement list have been substituted and # and ##
7820 processing has taken place, all placemarker preprocessing tokens are removed. Then, the
7821 resulting preprocessing token sequence is rescanned, along with all subsequent
7822 preprocessing tokens of the source file, for more macro names to replace.
7823 <p><!--para 2 -->
7824 If the name of the macro being replaced is found during this scan of the replacement list
7825 (not including the rest of the source file's preprocessing tokens), it is not replaced.
7826 Furthermore, if any nested replacements encounter the name of the macro being replaced,
7827 it is not replaced. These nonreplaced macro name preprocessing tokens are no longer
7828 available for further replacement even if they are later (re)examined in contexts in which
7829 that macro name preprocessing token would otherwise have been replaced.
7830 <p><!--para 3 -->
7831 The resulting completely macro-replaced preprocessing token sequence is not processed
7832 as a preprocessing directive even if it resembles one, but all pragma unary operator
7836 <p><!--para 1 -->
7837 A macro definition lasts (independent of block structure) until a corresponding #undef
7838 directive is encountered or (if none is encountered) until the end of the preprocessing
7839 translation unit. Macro definitions have no significance after translation phase 4.
7840 <p><!--para 2 -->
7841 A preprocessing directive of the form
7842 <pre>
7843 # undef identifier new-line</pre>
7844 causes the specified identifier no longer to be defined as a macro name. It is ignored if
7845 the specified identifier is not currently defined as a macro name.
7846 <p><!--para 3 -->
7847 EXAMPLE 1 The simplest use of this facility is to define a ''manifest constant'', as in
7848 <pre>
7849 #define TABSIZE 100
7850 int table[TABSIZE];</pre>
7852 <p><!--para 4 -->
7853 EXAMPLE 2 The following defines a function-like macro whose value is the maximum of its arguments.
7854 It has the advantages of working for any compatible types of the arguments and of generating in-line code
7855 without the overhead of function calling. It has the disadvantages of evaluating one or the other of its
7856 arguments a second time (including side effects) and generating more code than a function if invoked
7857 several times. It also cannot have its address taken, as it has none.
7858 <pre>
7859 #define max(a, b) ((a) > (b) ? (a) : (b))</pre>
7860 The parentheses ensure that the arguments and the resulting expression are bound properly.
7861 <!--page 168 -->
7862 <p><!--para 5 -->
7863 EXAMPLE 3 To illustrate the rules for redefinition and reexamination, the sequence
7864 <pre>
7865 #define x 3
7866 #define f(a) f(x * (a))
7867 #undef x
7868 #define x 2
7869 #define g f
7870 #define z z[0]
7871 #define h g(~
7872 #define m(a) a(w)
7873 #define w 0,1
7874 #define t(a) a
7875 #define p() int
7876 #define q(x) x
7877 #define r(x,y) x ## y
7878 #define str(x) # x
7879 f(y+1) + f(f(z)) % t(t(g)(0) + t)(1);
7880 g(x+(3,4)-w) | h 5) & m
7881 (f)^m(m);
7882 p() i[q()] = { q(1), r(2,3), r(4,), r(,5), r(,) };
7883 char c[2][6] = { str(hello), str() };</pre>
7884 results in
7885 <pre>
7886 f(2 * (y+1)) + f(2 * (f(2 * (z[0])))) % f(2 * (0)) + t(1);
7887 f(2 * (2+(3,4)-0,1)) | f(2 * (~ 5)) & f(2 * (0,1))^m(0,1);
7888 int i[] = { 1, 23, 4, 5, };
7891 <p><!--para 6 -->
7892 EXAMPLE 4 To illustrate the rules for creating character string literals and concatenating tokens, the
7893 sequence
7894 <pre>
7895 #define str(s) # s
7896 #define xstr(s) str(s)
7898 x ## s, x ## t)
7899 #define INCFILE(n) vers ## n
7900 #define glue(a, b) a ## b
7901 #define xglue(a, b) glue(a, b)
7904 debug(1, 2);
7906 == 0) str(: @\n), s);
7907 #include xstr(INCFILE(2).h)
7908 glue(HIGH, LOW);
7909 xglue(HIGH, LOW)</pre>
7910 results in
7911 <!--page 169 -->
7912 <pre>
7914 fputs(
7916 s);
7920 or, after concatenation of the character string literals,
7921 <pre>
7923 fputs(
7925 s);
7929 Space around the # and ## tokens in the macro definition is optional.
7931 <p><!--para 7 -->
7932 EXAMPLE 5 To illustrate the rules for placemarker preprocessing tokens, the sequence
7933 <pre>
7934 #define t(x,y,z) x ## y ## z
7935 int j[] = { t(1,2,3), t(,4,5), t(6,,7), t(8,9,),
7936 t(10,,), t(,11,), t(,,12), t(,,) };</pre>
7937 results in
7938 <pre>
7939 int j[] = { 123, 45, 67, 89,
7940 10, 11, 12, };</pre>
7942 <p><!--para 8 -->
7943 EXAMPLE 6 To demonstrate the redefinition rules, the following sequence is valid.
7944 <pre>
7945 #define OBJ_LIKE (1-1)
7946 #define OBJ_LIKE /* white space */ (1-1) /* other */
7947 #define FUNC_LIKE(a) ( a )
7948 #define FUNC_LIKE( a )( /* note the white space */ \
7949 a /* other stuff on this line
7950 */ )</pre>
7951 But the following redefinitions are invalid:
7952 <pre>
7953 #define OBJ_LIKE (0) // different token sequence
7954 #define OBJ_LIKE (1 - 1) // different white space
7955 #define FUNC_LIKE(b) ( a ) // different parameter usage
7956 #define FUNC_LIKE(b) ( b ) // different parameter spelling</pre>
7958 <p><!--para 9 -->
7959 EXAMPLE 7 Finally, to show the variable argument list macro facilities:
7960 <!--page 170 -->
7961 <pre>
7962 #define debug(...) fprintf(stderr, __VA_ARGS__)
7963 #define showlist(...) puts(#__VA_ARGS__)
7964 #define report(test, ...) ((test)?puts(#test):\
7965 printf(__VA_ARGS__))
7968 showlist(The first, second, and third items.);
7970 results in
7971 <pre>
7980 <h6>Constraints</h6>
7981 <p><!--para 1 -->
7982 The string literal of a #line directive, if present, shall be a character string literal.
7983 <h6>Semantics</h6>
7984 <p><!--para 2 -->
7985 The line number of the current source line is one greater than the number of new-line
7986 characters read or introduced in translation phase 1 (<a href="#5.1.1.2">5.1.1.2</a>) while processing the source
7987 file to the current token.
7988 <p><!--para 3 -->
7989 A preprocessing directive of the form
7990 <pre>
7991 # line digit-sequence new-line</pre>
7992 causes the implementation to behave as if the following sequence of source lines begins
7993 with a source line that has a line number as specified by the digit sequence (interpreted as
7994 a decimal integer). The digit sequence shall not specify zero, nor a number greater than
7995 2147483647.
7996 <p><!--para 4 -->
7997 A preprocessing directive of the form
7998 <pre>
8000 sets the presumed line number similarly and changes the presumed name of the source
8001 file to be the contents of the character string literal.
8002 <p><!--para 5 -->
8003 A preprocessing directive of the form
8004 <pre>
8005 # line pp-tokens new-line</pre>
8006 (that does not match one of the two previous forms) is permitted. The preprocessing
8007 tokens after line on the directive are processed just as in normal text (each identifier
8008 currently defined as a macro name is replaced by its replacement list of preprocessing
8009 tokens). The directive resulting after all replacements shall match one of the two
8010 previous forms and is then processed as appropriate.
8011 <!--page 171 -->
8014 <h6>Semantics</h6>
8015 <p><!--para 1 -->
8016 A preprocessing directive of the form
8017 <pre>
8018 # error pp-tokensopt new-line</pre>
8019 causes the implementation to produce a diagnostic message that includes the specified
8020 sequence of preprocessing tokens.
8023 <h6>Semantics</h6>
8024 <p><!--para 1 -->
8025 A preprocessing directive of the form
8026 <pre>
8027 # pragma pp-tokensopt new-line</pre>
8028 where the preprocessing token STDC does not immediately follow pragma in the
8029 directive (prior to any macro replacement)<sup><a href="#note152"><b>152)</b></a></sup> causes the implementation to behave in an
8030 implementation-defined manner. The behavior might cause translation to fail or cause the
8031 translator or the resulting program to behave in a non-conforming manner. Any such
8032 pragma that is not recognized by the implementation is ignored.
8033 <p><!--para 2 -->
8034 If the preprocessing token STDC does immediately follow pragma in the directive (prior
8035 to any macro replacement), then no macro replacement is performed on the directive, and
8036 the directive shall have one of the following forms<sup><a href="#note153"><b>153)</b></a></sup> whose meanings are described
8037 elsewhere:
8038 <pre>
8039 #pragma STDC FP_CONTRACT on-off-switch
8040 #pragma STDC FENV_ACCESS on-off-switch
8041 #pragma STDC CX_LIMITED_RANGE on-off-switch
8042 on-off-switch: one of
8043 ON OFF DEFAULT</pre>
8044 <p><b> Forward references</b>: the FP_CONTRACT pragma (<a href="#7.12.2">7.12.2</a>), the FENV_ACCESS pragma
8050 <!--page 172 -->
8052 <h6>footnotes</h6>
8053 <p><small><a name="note152" href="#note152">152)</a> An implementation is not required to perform macro replacement in pragmas, but it is permitted
8054 except for in standard pragmas (where STDC immediately follows pragma). If the result of macro
8055 replacement in a non-standard pragma has the same form as a standard pragma, the behavior is still
8056 implementation-defined; an implementation is permitted to behave as if it were the standard pragma,
8057 but is not required to.
8058 </small>
8059 <p><small><a name="note153" href="#note153">153)</a> See ''future language directions'' (<a href="#6.11.8">6.11.8</a>).
8060 </small>
8063 <h6>Semantics</h6>
8064 <p><!--para 1 -->
8065 A preprocessing directive of the form
8066 <pre>
8067 # new-line</pre>
8068 has no effect.
8071 <p><!--para 1 -->
8072 The following macro names<sup><a href="#note154"><b>154)</b></a></sup> shall be defined by the implementation:
8073 __DATE__ The date of translation of the preprocessing translation unit: a character
8074 <pre>
8076 months are the same as those generated by the asctime function, and the
8077 first character of dd is a space character if the value is less than 10. If the
8078 date of translation is not available, an implementation-defined valid date
8079 shall be supplied.</pre>
8080 __FILE__ The presumed name of the current source file (a character string literal).<sup><a href="#note155"><b>155)</b></a></sup>
8081 __LINE__ The presumed line number (within the current source file) of the current
8082 <pre>
8083 source line (an integer constant).155)</pre>
8084 __STDC__ The integer constant 1, intended to indicate a conforming implementation.
8085 __STDC_HOSTED__ The integer constant 1 if the implementation is a hosted
8086 <pre>
8087 implementation or the integer constant 0 if it is not.</pre>
8088 __STDC_MB_MIGHT_NEQ_WC__ The integer constant 1, intended to indicate that, in
8089 <pre>
8090 the encoding for wchar_t, a member of the basic character set need not
8091 have a code value equal to its value when used as the lone character in an
8092 integer character constant.</pre>
8094 __TIME__ The time of translation of the preprocessing translation unit: a character
8095 <pre>
8097 asctime function. If the time of translation is not available, an
8098 implementation-defined valid time shall be supplied.</pre>
8102 <!--page 173 -->
8103 <p><!--para 2 -->
8104 The following macro names are conditionally defined by the implementation:
8105 __STDC_IEC_559__ The integer constant 1, intended to indicate conformance to the
8106 <pre>
8108 __STDC_IEC_559_COMPLEX__ The integer constant 1, intended to indicate
8109 <pre>
8111 compatible complex arithmetic).</pre>
8112 __STDC_ISO_10646__ An integer constant of the form yyyymmL (for example,
8113 <p><!--para 3 -->
8114 <pre>
8115 199712L). If this symbol is defined, then every character in the Unicode
8116 required set, when stored in an object of type wchar_t, has the same
8117 value as the short identifier of that character. The Unicode required set
8118 consists of all the characters that are defined by ISO/IEC 10646, along with
8119 all amendments and technical corrigenda, as of the specified year and
8120 month.</pre>
8121 The values of the predefined macros (except for __FILE__ and __LINE__) remain
8122 constant throughout the translation unit.
8123 <p><!--para 4 -->
8124 None of these macro names, nor the identifier defined, shall be the subject of a
8125 #define or a #undef preprocessing directive. Any other predefined macro names
8126 shall begin with a leading underscore followed by an uppercase letter or a second
8127 underscore.
8128 <p><!--para 5 -->
8129 The implementation shall not predefine the macro __cplusplus, nor shall it define it
8130 in any standard header.
8131 <p><b> Forward references</b>: the asctime function (<a href="#7.23.3.1">7.23.3.1</a>), standard headers (<a href="#7.1.2">7.1.2</a>).
8133 <h6>footnotes</h6>
8134 <p><small><a name="note154" href="#note154">154)</a> See ''future language directions'' (<a href="#6.11.9">6.11.9</a>).
8135 </small>
8136 <p><small><a name="note155" href="#note155">155)</a> The presumed source file name and line number can be changed by the #line directive.
8137 </small>
8138 <p><small><a name="note156" href="#note156">156)</a> This macro was not specified in ISO/IEC 9899:1990 and was specified as 199409L in
8139 ISO/IEC 9899/AMD1:1995. The intention is that this will remain an integer constant of type long
8140 int that is increased with each revision of this International Standard.
8141 </small>
8144 <h6>Semantics</h6>
8145 <p><!--para 1 -->
8146 A unary operator expression of the form:
8147 <pre>
8148 _Pragma ( string-literal )</pre>
8149 is processed as follows: The string literal is destringized by deleting the L prefix, if
8150 present, deleting the leading and trailing double-quotes, replacing each escape sequence
8151 \" by a double-quote, and replacing each escape sequence \\ by a single backslash. The
8152 resulting sequence of characters is processed through translation phase 3 to produce
8153 preprocessing tokens that are executed as if they were the pp-tokens in a pragma
8154 directive. The original four preprocessing tokens in the unary operator expression are
8155 removed.
8157 EXAMPLE A directive of the form:
8158 <pre>
8160 can also be expressed as:
8161 <!--page 174 -->
8162 <pre>
8164 The latter form is processed in the same way whether it appears literally as shown, or results from macro
8165 replacement, as in:
8166 <!--page 175 -->
8167 <pre>
8168 #define LISTING(x) PRAGMA(listing on #x)
8169 #define PRAGMA(x) _Pragma(#x)
8170 LISTING ( ..\listing.dir )</pre>
8176 Future standardization may include additional floating-point types, including those with
8177 greater range, precision, or both than long double.
8181 Declaring an identifier with internal linkage at file scope without the static storage-
8182 class specifier is an obsolescent feature.
8186 Restriction of the significance of an external name to fewer than 255 characters
8187 (considering each universal character name or extended source character as a single
8188 character) is an obsolescent feature that is a concession to existing implementations.
8192 Lowercase letters as escape sequences are reserved for future standardization. Other
8193 characters may be used in extensions.
8197 The placement of a storage-class specifier other than at the beginning of the declaration
8198 specifiers in a declaration is an obsolescent feature.
8202 The use of function declarators with empty parentheses (not prototype-format parameter
8203 type declarators) is an obsolescent feature.
8207 The use of function definitions with separate parameter identifier and declaration lists
8208 (not prototype-format parameter type and identifier declarators) is an obsolescent feature.
8212 Pragmas whose first preprocessing token is STDC are reserved for future standardization.
8216 Macro names beginning with __STDC_ are reserved for future standardization.
8217 <!--page 176 -->
8226 A string is a contiguous sequence of characters terminated by and including the first null
8227 character. The term multibyte string is sometimes used instead to emphasize special
8228 processing given to multibyte characters contained in the string or to avoid confusion
8229 with a wide string. A pointer to a string is a pointer to its initial (lowest addressed)
8230 character. The length of a string is the number of bytes preceding the null character and
8231 the value of a string is the sequence of the values of the contained characters, in order.
8233 The decimal-point character is the character used by functions that convert floating-point
8234 numbers to or from character sequences to denote the beginning of the fractional part of
8235 such character sequences.<sup><a href="#note157"><b>157)</b></a></sup> It is represented in the text and examples by a period, but
8236 may be changed by the setlocale function.
8238 A null wide character is a wide character with code value zero.
8240 A wide string is a contiguous sequence of wide characters terminated by and including
8241 the first null wide character. A pointer to a wide string is a pointer to its initial (lowest
8242 addressed) wide character. The length of a wide string is the number of wide characters
8243 preceding the null wide character and the value of a wide string is the sequence of code
8244 values of the contained wide characters, in order.
8246 A shift sequence is a contiguous sequence of bytes within a multibyte string that
8247 (potentially) causes a change in shift state (see <a href="#5.2.1.2">5.2.1.2</a>). A shift sequence shall not have a
8248 corresponding wide character; it is instead taken to be an adjunct to an adjacent multibyte
8250 <p><b> Forward references</b>: character handling (<a href="#7.4">7.4</a>), the setlocale function (<a href="#7.11.1.1">7.11.1.1</a>).
8255 <!--page 177 -->
8258 <p><small><a name="note157" href="#note157">157)</a> The functions that make use of the decimal-point character are the numeric conversion functions
8259 (<a href="#7.20.1">7.20.1</a>, <a href="#7.24.4.1">7.24.4.1</a>) and the formatted input/output functions (<a href="#7.19.6">7.19.6</a>, <a href="#7.24.2">7.24.2</a>).
8260 </small>
8261 <p><small><a name="note158" href="#note158">158)</a> For state-dependent encodings, the values for MB_CUR_MAX and MB_LEN_MAX shall thus be large
8262 enough to count all the bytes in any complete multibyte character plus at least one adjacent shift
8263 sequence of maximum length. Whether these counts provide for more than one shift sequence is the
8264 implementation's choice.
8265 </small>
8269 Each library function is declared, with a type that includes a prototype, in a header,<sup><a href="#note159"><b>159)</b></a></sup>
8270 whose contents are made available by the #include preprocessing directive. The
8271 header declares a set of related functions, plus any necessary types and additional macros
8272 needed to facilitate their use. Declarations of types described in this clause shall not
8273 include type qualifiers, unless explicitly stated otherwise.
8275 The standard headers are
8277 <pre>
8278 <a href="#7.2"><assert.h></a> <a href="#7.8"><inttypes.h></a> <a href="#7.14"><signal.h></a> <a href="#7.20"><stdlib.h></a>
8279 <a href="#7.3"><complex.h></a> <a href="#7.9"><iso646.h></a> <a href="#7.15"><stdarg.h></a> <a href="#7.21"><string.h></a>
8280 <a href="#7.4"><ctype.h></a> <a href="#7.10"><limits.h></a> <a href="#7.16"><stdbool.h></a> <a href="#7.22"><tgmath.h></a>
8281 <a href="#7.5"><errno.h></a> <a href="#7.11"><locale.h></a> <a href="#7.17"><stddef.h></a> <a href="#7.23"><time.h></a>
8282 <a href="#7.6"><fenv.h></a> <a href="#7.12"><math.h></a> <a href="#7.18"><stdint.h></a> <a href="#7.24"><wchar.h></a>
8283 <a href="#7.7"><float.h></a> <a href="#7.13"><setjmp.h></a> <a href="#7.19"><stdio.h></a> <a href="#7.25"><wctype.h></a></pre>
8285 provided as part of the implementation, is placed in any of the standard places that are
8286 searched for included source files, the behavior is undefined.
8288 Standard headers may be included in any order; each may be included more than once in
8289 a given scope, with no effect different from being included only once, except that the
8290 effect of including <a href="#7.2"><assert.h></a> depends on the definition of NDEBUG (see <a href="#7.2">7.2</a>). If
8291 used, a header shall be included outside of any external declaration or definition, and it
8292 shall first be included before the first reference to any of the functions or objects it
8293 declares, or to any of the types or macros it defines. However, if an identifier is declared
8294 or defined in more than one header, the second and subsequent associated headers may be
8295 included after the initial reference to the identifier. The program shall not have any
8296 macros with names lexically identical to keywords currently defined prior to the
8297 inclusion.
8299 Any definition of an object-like macro described in this clause shall expand to code that is
8300 fully protected by parentheses where necessary, so that it groups in an arbitrary
8301 expression as if it were a single identifier.
8303 Any declaration of a library function shall have external linkage.
8311 <!--page 178 -->
8314 <p><small><a name="note159" href="#note159">159)</a> A header is not necessarily a source file, nor are the < and > delimited sequences in header names
8315 necessarily valid source file names.
8316 </small>
8320 Each header declares or defines all identifiers listed in its associated subclause, and
8321 optionally declares or defines identifiers listed in its associated future library directions
8322 subclause and identifiers which are always reserved either for any use or for use as file
8323 scope identifiers.
8324 <ul>
8325 <li> All identifiers that begin with an underscore and either an uppercase letter or another
8326 underscore are always reserved for any use.
8327 <li> All identifiers that begin with an underscore are always reserved for use as identifiers
8328 with file scope in both the ordinary and tag name spaces.
8329 <li> Each macro name in any of the following subclauses (including the future library
8330 directions) is reserved for use as specified if any of its associated headers is included;
8332 <li> All identifiers with external linkage in any of the following subclauses (including the
8333 future library directions) are always reserved for use as identifiers with external
8335 <li> Each identifier with file scope listed in any of the following subclauses (including the
8336 future library directions) is reserved for use as a macro name and as an identifier with
8337 file scope in the same name space if any of its associated headers is included.
8338 </ul>
8340 No other identifiers are reserved. If the program declares or defines an identifier in a
8341 context in which it is reserved (other than as allowed by <a href="#7.1.4">7.1.4</a>), or defines a reserved
8342 identifier as a macro name, the behavior is undefined.
8344 If the program removes (with #undef) any macro definition of an identifier in the first
8345 group listed above, the behavior is undefined.
8348 <p><small><a name="note160" href="#note160">160)</a> The list of reserved identifiers with external linkage includes errno, math_errhandling,
8349 setjmp, and va_end.
8350 </small>
8354 Each of the following statements applies unless explicitly stated otherwise in the detailed
8355 descriptions that follow: If an argument to a function has an invalid value (such as a value
8356 outside the domain of the function, or a pointer outside the address space of the program,
8357 or a null pointer, or a pointer to non-modifiable storage when the corresponding
8358 parameter is not const-qualified) or a type (after promotion) not expected by a function
8359 with variable number of arguments, the behavior is undefined. If a function argument is
8360 described as being an array, the pointer actually passed to the function shall have a value
8361 such that all address computations and accesses to objects (that would be valid if the
8362 pointer did point to the first element of such an array) are in fact valid. Any function
8363 declared in a header may be additionally implemented as a function-like macro defined in
8365 <!--page 179 -->
8366 the header, so if a library function is declared explicitly when its header is included, one
8367 of the techniques shown below can be used to ensure the declaration is not affected by
8368 such a macro. Any macro definition of a function can be suppressed locally by enclosing
8369 the name of the function in parentheses, because the name is then not followed by the left
8370 parenthesis that indicates expansion of a macro function name. For the same syntactic
8371 reason, it is permitted to take the address of a library function even if it is also defined as
8372 a macro.<sup><a href="#note161"><b>161)</b></a></sup> The use of #undef to remove any macro definition will also ensure that an
8373 actual function is referred to. Any invocation of a library function that is implemented as
8374 a macro shall expand to code that evaluates each of its arguments exactly once, fully
8375 protected by parentheses where necessary, so it is generally safe to use arbitrary
8376 expressions as arguments.<sup><a href="#note162"><b>162)</b></a></sup> Likewise, those function-like macros described in the
8377 following subclauses may be invoked in an expression anywhere a function with a
8378 compatible return type could be called.<sup><a href="#note163"><b>163)</b></a></sup> All object-like macros listed as expanding to
8379 integer constant expressions shall additionally be suitable for use in #if preprocessing
8380 directives.
8382 Provided that a library function can be declared without reference to any type defined in a
8383 header, it is also permissible to declare the function and use it without including its
8384 associated header.
8386 There is a sequence point immediately before a library function returns.
8388 The functions in the standard library are not guaranteed to be reentrant and may modify
8393 <!--page 180 -->
8395 EXAMPLE The function atoi may be used in any of several ways:
8396 <ul>
8397 <li> by use of its associated header (possibly generating a macro expansion)
8398 <pre>
8400 const char *str;
8401 /* ... */
8402 i = atoi(str);</pre>
8403 <li> by use of its associated header (assuredly generating a true function reference)
8404 <pre>
8406 #undef atoi
8407 const char *str;
8408 /* ... */
8409 i = atoi(str);</pre>
8410 or
8411 <pre>
8413 const char *str;
8414 /* ... */
8415 i = (atoi)(str);</pre>
8416 <li> by explicit declaration
8417 <!--page 181 -->
8418 <pre>
8419 extern int atoi(const char *);
8420 const char *str;
8421 /* ... */
8422 i = atoi(str);</pre>
8423 </ul>
8426 <p><small><a name="note161" href="#note161">161)</a> This means that an implementation shall provide an actual function for each library function, even if it
8427 also provides a macro for that function.
8428 </small>
8429 <p><small><a name="note162" href="#note162">162)</a> Such macros might not contain the sequence points that the corresponding function calls do.
8430 </small>
8431 <p><small><a name="note163" href="#note163">163)</a> Because external identifiers and some macro names beginning with an underscore are reserved,
8432 implementations may provide special semantics for such names. For example, the identifier
8433 _BUILTIN_abs could be used to indicate generation of in-line code for the abs function. Thus, the
8434 appropriate header could specify
8436 <pre>
8437 #define abs(x) _BUILTIN_abs(x)</pre>
8438 for a compiler whose code generator will accept it.
8439 In this manner, a user desiring to guarantee that a given library function such as abs will be a genuine
8440 function may write
8442 <pre>
8443 #undef abs</pre>
8444 whether the implementation's header provides a macro implementation of abs or a built-in
8445 implementation. The prototype for the function, which precedes and is hidden by any macro
8446 definition, is thereby revealed also.
8447 </small>
8448 <p><small><a name="note164" href="#note164">164)</a> Thus, a signal handler cannot, in general, call standard library functions.
8449 </small>
8453 The header <a href="#7.2"><assert.h></a> defines the assert macro and refers to another macro,
8454 <pre>
8455 NDEBUG</pre>
8456 which is not defined by <a href="#7.2"><assert.h></a>. If NDEBUG is defined as a macro name at the
8457 point in the source file where <a href="#7.2"><assert.h></a> is included, the assert macro is defined
8458 simply as
8459 <pre>
8461 The assert macro is redefined according to the current state of NDEBUG each time that
8464 The assert macro shall be implemented as a macro, not as an actual function. If the
8465 macro definition is suppressed in order to access an actual function, the behavior is
8466 undefined.
8473 <pre>
8475 void assert(scalar expression);</pre>
8478 The assert macro puts diagnostic tests into programs; it expands to a void expression.
8479 When it is executed, if expression (which shall have a scalar type) is false (that is,
8480 compares equal to 0), the assert macro writes information about the particular call that
8481 failed (including the text of the argument, the name of the source file, the source line
8482 number, and the name of the enclosing function -- the latter are respectively the values of
8483 the preprocessing macros __FILE__ and __LINE__ and of the identifier
8484 __func__) on the standard error stream in an implementation-defined format.<sup><a href="#note165"><b>165)</b></a></sup> It
8485 then calls the abort function.
8488 The assert macro returns no value.
8494 <!--page 182 -->
8498 Assertion failed: expression, function abc, file xyz, line nnn.
8499 </small>
8505 The header <a href="#7.3"><complex.h></a> defines macros and declares functions that support complex
8506 arithmetic.<sup><a href="#note166"><b>166)</b></a></sup> Each synopsis specifies a family of functions consisting of a principal
8507 function with one or more double complex parameters and a double complex or
8508 double return value; and other functions with the same name but with f and l suffixes
8509 which are corresponding functions with float and long double parameters and
8510 return values.
8512 The macro
8513 <pre>
8514 complex</pre>
8515 expands to _Complex; the macro
8516 <pre>
8517 _Complex_I</pre>
8518 expands to a constant expression of type const float _Complex, with the value of
8521 The macros
8522 <pre>
8523 imaginary</pre>
8524 and
8525 <pre>
8526 _Imaginary_I</pre>
8527 are defined if and only if the implementation supports imaginary types;<sup><a href="#note168"><b>168)</b></a></sup> if defined,
8528 they expand to _Imaginary and a constant expression of type const float
8529 _Imaginary with the value of the imaginary unit.
8531 The macro
8532 <pre>
8533 I</pre>
8534 expands to either _Imaginary_I or _Complex_I. If _Imaginary_I is not
8535 defined, I shall expand to _Complex_I.
8537 Notwithstanding the provisions of <a href="#7.1.3">7.1.3</a>, a program may undefine and perhaps then
8538 redefine the macros complex, imaginary, and I.
8539 <p><b> Forward references</b>: IEC 60559-compatible complex arithmetic (<a href="#G">annex G</a>).
8543 <!--page 183 -->
8546 <p><small><a name="note166" href="#note166">166)</a> See ''future library directions'' (<a href="#7.26.1">7.26.1</a>).
8547 </small>
8548 <p><small><a name="note167" href="#note167">167)</a> The imaginary unit is a number i such that i 2 = -1.
8549 </small>
8550 <p><small><a name="note168" href="#note168">168)</a> A specification for imaginary types is in informative <a href="#G">annex G</a>.
8551 </small>
8555 Values are interpreted as radians, not degrees. An implementation may set errno but is
8556 not required to.
8560 Some of the functions below have branch cuts, across which the function is
8561 discontinuous. For implementations with a signed zero (including all IEC 60559
8562 implementations) that follow the specifications of <a href="#G">annex G</a>, the sign of zero distinguishes
8563 one side of a cut from another so the function is continuous (except for format
8564 limitations) as the cut is approached from either side. For example, for the square root
8565 function, which has a branch cut along the negative real axis, the top of the cut, with
8566 imaginary part +0, maps to the positive imaginary axis, and the bottom of the cut, with
8567 imaginary part -0, maps to the negative imaginary axis.
8569 Implementations that do not support a signed zero (see <a href="#F">annex F</a>) cannot distinguish the
8570 sides of branch cuts. These implementations shall map a cut so the function is continuous
8571 as the cut is approached coming around the finite endpoint of the cut in a counter
8572 clockwise direction. (Branch cuts for the functions specified here have just one finite
8573 endpoint.) For example, for the square root function, coming counter clockwise around
8574 the finite endpoint of the cut along the negative real axis approaches the cut from above,
8575 so the cut maps to the positive imaginary axis.
8580 <pre>
8582 #pragma STDC CX_LIMITED_RANGE on-off-switch</pre>
8585 The usual mathematical formulas for complex multiply, divide, and absolute value are
8586 problematic because of their treatment of infinities and because of undue overflow and
8587 underflow. The CX_LIMITED_RANGE pragma can be used to inform the
8588 implementation that (where the state is ''on'') the usual mathematical formulas are
8589 acceptable.<sup><a href="#note169"><b>169)</b></a></sup> The pragma can occur either outside external declarations or preceding all
8590 explicit declarations and statements inside a compound statement. When outside external
8592 <!--page 184 -->
8593 declarations, the pragma takes effect from its occurrence until another
8594 CX_LIMITED_RANGE pragma is encountered, or until the end of the translation unit.
8595 When inside a compound statement, the pragma takes effect from its occurrence until
8596 another CX_LIMITED_RANGE pragma is encountered (including within a nested
8597 compound statement), or until the end of the compound statement; at the end of a
8598 compound statement the state for the pragma is restored to its condition just before the
8599 compound statement. If this pragma is used in any other context, the behavior is
8600 undefined. The default state for the pragma is ''off''.
8603 <p><small><a name="note169" href="#note169">169)</a> The purpose of the pragma is to allow the implementation to use the formulas:
8605 <pre>
8606 (x + iy) x (u + iv) = (xu - yv) + i(yu + xv)
8607 (x + iy) / (u + iv) = [(xu + yv) + i(yu - xv)]/(u2 + v 2 )
8609 ???????????????</pre>
8610 where the programmer can determine they are safe.
8611 </small>
8618 <pre>
8620 double complex cacos(double complex z);
8621 float complex cacosf(float complex z);
8622 long double complex cacosl(long double complex z);</pre>
8625 The cacos functions compute the complex arc cosine of z, with branch cuts outside the
8629 The cacos functions return the complex arc cosine value, in the range of a strip
8630 mathematically unbounded along the imaginary axis and in the interval [0, pi ] along the
8631 real axis.
8636 <pre>
8638 double complex casin(double complex z);
8639 float complex casinf(float complex z);
8640 long double complex casinl(long double complex z);</pre>
8643 The casin functions compute the complex arc sine of z, with branch cuts outside the
8647 The casin functions return the complex arc sine value, in the range of a strip
8649 along the real axis.
8650 <!--page 185 -->
8655 <pre>
8657 double complex catan(double complex z);
8658 float complex catanf(float complex z);
8659 long double complex catanl(long double complex z);</pre>
8662 The catan functions compute the complex arc tangent of z, with branch cuts outside the
8663 interval [-i, +i] along the imaginary axis.
8666 The catan functions return the complex arc tangent value, in the range of a strip
8668 along the real axis.
8673 <pre>
8675 double complex ccos(double complex z);
8676 float complex ccosf(float complex z);
8677 long double complex ccosl(long double complex z);</pre>
8680 The ccos functions compute the complex cosine of z.
8683 The ccos functions return the complex cosine value.
8688 <pre>
8690 double complex csin(double complex z);
8691 float complex csinf(float complex z);
8692 long double complex csinl(long double complex z);</pre>
8695 The csin functions compute the complex sine of z.
8698 The csin functions return the complex sine value.
8699 <!--page 186 -->
8704 <pre>
8706 double complex ctan(double complex z);
8707 float complex ctanf(float complex z);
8708 long double complex ctanl(long double complex z);</pre>
8711 The ctan functions compute the complex tangent of z.
8714 The ctan functions return the complex tangent value.
8721 <pre>
8723 double complex cacosh(double complex z);
8724 float complex cacoshf(float complex z);
8725 long double complex cacoshl(long double complex z);</pre>
8728 The cacosh functions compute the complex arc hyperbolic cosine of z, with a branch
8729 cut at values less than 1 along the real axis.
8732 The cacosh functions return the complex arc hyperbolic cosine value, in the range of a
8733 half-strip of non-negative values along the real axis and in the interval [-ipi , +ipi ] along
8734 the imaginary axis.
8739 <pre>
8741 double complex casinh(double complex z);
8742 float complex casinhf(float complex z);
8743 long double complex casinhl(long double complex z);</pre>
8746 The casinh functions compute the complex arc hyperbolic sine of z, with branch cuts
8747 outside the interval [-i, +i] along the imaginary axis.
8748 <!--page 187 -->
8751 The casinh functions return the complex arc hyperbolic sine value, in the range of a
8753 along the imaginary axis.
8758 <pre>
8760 double complex catanh(double complex z);
8761 float complex catanhf(float complex z);
8762 long double complex catanhl(long double complex z);</pre>
8765 The catanh functions compute the complex arc hyperbolic tangent of z, with branch
8769 The catanh functions return the complex arc hyperbolic tangent value, in the range of a
8771 along the imaginary axis.
8776 <pre>
8778 double complex ccosh(double complex z);
8779 float complex ccoshf(float complex z);
8780 long double complex ccoshl(long double complex z);</pre>
8783 The ccosh functions compute the complex hyperbolic cosine of z.
8786 The ccosh functions return the complex hyperbolic cosine value.
8791 <!--page 188 -->
8792 <pre>
8794 double complex csinh(double complex z);
8795 float complex csinhf(float complex z);
8796 long double complex csinhl(long double complex z);</pre>
8799 The csinh functions compute the complex hyperbolic sine of z.
8802 The csinh functions return the complex hyperbolic sine value.
8807 <pre>
8809 double complex ctanh(double complex z);
8810 float complex ctanhf(float complex z);
8811 long double complex ctanhl(long double complex z);</pre>
8814 The ctanh functions compute the complex hyperbolic tangent of z.
8817 The ctanh functions return the complex hyperbolic tangent value.
8824 <pre>
8826 double complex cexp(double complex z);
8827 float complex cexpf(float complex z);
8828 long double complex cexpl(long double complex z);</pre>
8831 The cexp functions compute the complex base-e exponential of z.
8834 The cexp functions return the complex base-e exponential value.
8839 <!--page 189 -->
8840 <pre>
8842 double complex clog(double complex z);
8843 float complex clogf(float complex z);
8844 long double complex clogl(long double complex z);</pre>
8847 The clog functions compute the complex natural (base-e) logarithm of z, with a branch
8848 cut along the negative real axis.
8851 The clog functions return the complex natural logarithm value, in the range of a strip
8852 mathematically unbounded along the real axis and in the interval [-ipi , +ipi ] along the
8853 imaginary axis.
8860 <pre>
8862 double cabs(double complex z);
8863 float cabsf(float complex z);
8864 long double cabsl(long double complex z);</pre>
8867 The cabs functions compute the complex absolute value (also called norm, modulus, or
8868 magnitude) of z.
8871 The cabs functions return the complex absolute value.
8876 <pre>
8878 double complex cpow(double complex x, double complex y);
8879 float complex cpowf(float complex x, float complex y);
8880 long double complex cpowl(long double complex x,
8881 long double complex y);</pre>
8884 The cpow functions compute the complex power function xy , with a branch cut for the
8885 first parameter along the negative real axis.
8888 The cpow functions return the complex power function value.
8889 <!--page 190 -->
8894 <pre>
8896 double complex csqrt(double complex z);
8897 float complex csqrtf(float complex z);
8898 long double complex csqrtl(long double complex z);</pre>
8901 The csqrt functions compute the complex square root of z, with a branch cut along the
8902 negative real axis.
8905 The csqrt functions return the complex square root value, in the range of the right half-
8906 plane (including the imaginary axis).
8913 <pre>
8915 double carg(double complex z);
8916 float cargf(float complex z);
8917 long double cargl(long double complex z);</pre>
8920 The carg functions compute the argument (also called phase angle) of z, with a branch
8921 cut along the negative real axis.
8924 The carg functions return the value of the argument in the interval [-pi , +pi ].
8929 <!--page 191 -->
8930 <pre>
8932 double cimag(double complex z);
8933 float cimagf(float complex z);
8934 long double cimagl(long double complex z);</pre>
8937 The cimag functions compute the imaginary part of z.<sup><a href="#note170"><b>170)</b></a></sup>
8940 The cimag functions return the imaginary part value (as a real).
8943 <p><small><a name="note170" href="#note170">170)</a> For a variable z of complex type, z == creal(z) + cimag(z)*I.
8944 </small>
8949 <pre>
8951 double complex conj(double complex z);
8952 float complex conjf(float complex z);
8953 long double complex conjl(long double complex z);</pre>
8956 The conj functions compute the complex conjugate of z, by reversing the sign of its
8957 imaginary part.
8960 The conj functions return the complex conjugate value.
8965 <pre>
8967 double complex cproj(double complex z);
8968 float complex cprojf(float complex z);
8969 long double complex cprojl(long double complex z);</pre>
8972 The cproj functions compute a projection of z onto the Riemann sphere: z projects to
8973 z except that all complex infinities (even those with one infinite part and one NaN part)
8974 project to positive infinity on the real axis. If z has an infinite part, then cproj(z) is
8975 equivalent to
8976 <pre>
8980 The cproj functions return the value of the projection onto the Riemann sphere.
8985 <!--page 192 -->
8990 <pre>
8992 double creal(double complex z);
8993 float crealf(float complex z);
8994 long double creall(long double complex z);</pre>
9000 The creal functions return the real part value.
9005 <!--page 193 -->
9008 <p><small><a name="note171" href="#note171">171)</a> For a variable z of complex type, z == creal(z) + cimag(z)*I.
9009 </small>
9013 The header <a href="#7.4"><ctype.h></a> declares several functions useful for classifying and mapping
9014 characters.<sup><a href="#note172"><b>172)</b></a></sup> In all cases the argument is an int, the value of which shall be
9015 representable as an unsigned char or shall equal the value of the macro EOF. If the
9016 argument has any other value, the behavior is undefined.
9018 The behavior of these functions is affected by the current locale. Those functions that
9019 have locale-specific aspects only when not in the "C" locale are noted below.
9021 The term printing character refers to a member of a locale-specific set of characters, each
9022 of which occupies one printing position on a display device; the term control character
9023 refers to a member of a locale-specific set of characters that are not printing
9024 characters.<sup><a href="#note173"><b>173)</b></a></sup> All letters and digits are printing characters.
9025 <p><b> Forward references</b>: EOF (<a href="#7.19.1">7.19.1</a>), localization (<a href="#7.11">7.11</a>).
9028 <p><small><a name="note172" href="#note172">172)</a> See ''future library directions'' (<a href="#7.26.2">7.26.2</a>).
9029 </small>
9030 <p><small><a name="note173" href="#note173">173)</a> In an implementation that uses the seven-bit US ASCII character set, the printing characters are those
9031 whose values lie from 0x20 (space) through 0x7E (tilde); the control characters are those whose
9033 </small>
9037 The functions in this subclause return nonzero (true) if and only if the value of the
9038 argument c conforms to that in the description of the function.
9043 <pre>
9045 int isalnum(int c);</pre>
9048 The isalnum function tests for any character for which isalpha or isdigit is true.
9053 <pre>
9055 int isalpha(int c);</pre>
9058 The isalpha function tests for any character for which isupper or islower is true,
9059 or any character that is one of a locale-specific set of alphabetic characters for which
9063 <!--page 194 -->
9064 none of iscntrl, isdigit, ispunct, or isspace is true.<sup><a href="#note174"><b>174)</b></a></sup> In the "C" locale,
9065 isalpha returns true only for the characters for which isupper or islower is true.
9068 <p><small><a name="note174" href="#note174">174)</a> The functions islower and isupper test true or false separately for each of these additional
9069 characters; all four combinations are possible.
9070 </small>
9075 <pre>
9077 int isblank(int c);</pre>
9080 The isblank function tests for any character that is a standard blank character or is one
9081 of a locale-specific set of characters for which isspace is true and that is used to
9082 separate words within a line of text. The standard blank characters are the following:
9083 space (' '), and horizontal tab ('\t'). In the "C" locale, isblank returns true only
9084 for the standard blank characters.
9089 <pre>
9091 int iscntrl(int c);</pre>
9094 The iscntrl function tests for any control character.
9099 <pre>
9101 int isdigit(int c);</pre>
9104 The isdigit function tests for any decimal-digit character (as defined in <a href="#5.2.1">5.2.1</a>).
9109 <pre>
9111 int isgraph(int c);</pre>
9116 <!--page 195 -->
9119 The isgraph function tests for any printing character except space (' ').
9124 <pre>
9126 int islower(int c);</pre>
9129 The islower function tests for any character that is a lowercase letter or is one of a
9130 locale-specific set of characters for which none of iscntrl, isdigit, ispunct, or
9131 isspace is true. In the "C" locale, islower returns true only for the lowercase
9137 <pre>
9139 int isprint(int c);</pre>
9142 The isprint function tests for any printing character including space (' ').
9147 <pre>
9149 int ispunct(int c);</pre>
9152 The ispunct function tests for any printing character that is one of a locale-specific set
9153 of punctuation characters for which neither isspace nor isalnum is true. In the "C"
9154 locale, ispunct returns true for every printing character for which neither isspace
9155 nor isalnum is true.
9160 <pre>
9162 int isspace(int c);</pre>
9165 The isspace function tests for any character that is a standard white-space character or
9166 is one of a locale-specific set of characters for which isalnum is false. The standard
9167 <!--page 196 -->
9168 white-space characters are the following: space (' '), form feed ('\f'), new-line
9169 ('\n'), carriage return ('\r'), horizontal tab ('\t'), and vertical tab ('\v'). In the
9170 "C" locale, isspace returns true only for the standard white-space characters.
9175 <pre>
9177 int isupper(int c);</pre>
9180 The isupper function tests for any character that is an uppercase letter or is one of a
9181 locale-specific set of characters for which none of iscntrl, isdigit, ispunct, or
9182 isspace is true. In the "C" locale, isupper returns true only for the uppercase
9188 <pre>
9190 int isxdigit(int c);</pre>
9193 The isxdigit function tests for any hexadecimal-digit character (as defined in <a href="#6.4.4.1">6.4.4.1</a>).
9200 <pre>
9202 int tolower(int c);</pre>
9205 The tolower function converts an uppercase letter to a corresponding lowercase letter.
9208 If the argument is a character for which isupper is true and there are one or more
9209 corresponding characters, as specified by the current locale, for which islower is true,
9210 the tolower function returns one of the corresponding characters (always the same one
9211 for any given locale); otherwise, the argument is returned unchanged.
9212 <!--page 197 -->
9217 <pre>
9219 int toupper(int c);</pre>
9222 The toupper function converts a lowercase letter to a corresponding uppercase letter.
9225 If the argument is a character for which islower is true and there are one or more
9226 corresponding characters, as specified by the current locale, for which isupper is true,
9227 the toupper function returns one of the corresponding characters (always the same one
9228 for any given locale); otherwise, the argument is returned unchanged.
9229 <!--page 198 -->
9233 The header <a href="#7.5"><errno.h></a> defines several macros, all relating to the reporting of error
9234 conditions.
9236 The macros are
9237 <pre>
9238 EDOM
9239 EILSEQ
9240 ERANGE</pre>
9241 which expand to integer constant expressions with type int, distinct positive values, and
9242 which are suitable for use in #if preprocessing directives; and
9243 <pre>
9244 errno</pre>
9245 which expands to a modifiable lvalue<sup><a href="#note175"><b>175)</b></a></sup> that has type int, the value of which is set to a
9246 positive error number by several library functions. It is unspecified whether errno is a
9247 macro or an identifier declared with external linkage. If a macro definition is suppressed
9248 in order to access an actual object, or a program defines an identifier with the name
9249 errno, the behavior is undefined.
9251 The value of errno is zero at program startup, but is never set to zero by any library
9252 function.<sup><a href="#note176"><b>176)</b></a></sup> The value of errno may be set to nonzero by a library function call
9253 whether or not there is an error, provided the use of errno is not documented in the
9254 description of the function in this International Standard.
9256 Additional macro definitions, beginning with E and a digit or E and an uppercase
9257 letter,<sup><a href="#note177"><b>177)</b></a></sup> may also be specified by the implementation.
9262 <!--page 199 -->
9265 <p><small><a name="note175" href="#note175">175)</a> The macro errno need not be the identifier of an object. It might expand to a modifiable lvalue
9266 resulting from a function call (for example, *errno()).
9267 </small>
9268 <p><small><a name="note176" href="#note176">176)</a> Thus, a program that uses errno for error checking should set it to zero before a library function call,
9269 then inspect it before a subsequent library function call. Of course, a library function can save the
9270 value of errno on entry and then set it to zero, as long as the original value is restored if errno's
9271 value is still zero just before the return.
9272 </small>
9273 <p><small><a name="note177" href="#note177">177)</a> See ''future library directions'' (<a href="#7.26.3">7.26.3</a>).
9274 </small>
9278 The header <a href="#7.6"><fenv.h></a> declares two types and several macros and functions to provide
9279 access to the floating-point environment. The floating-point environment refers
9280 collectively to any floating-point status flags and control modes supported by the
9281 implementation.<sup><a href="#note178"><b>178)</b></a></sup> A floating-point status flag is a system variable whose value is set
9282 (but never cleared) when a floating-point exception is raised, which occurs as a side effect
9283 of exceptional floating-point arithmetic to provide auxiliary information.<sup><a href="#note179"><b>179)</b></a></sup> A floating-
9284 point control mode is a system variable whose value may be set by the user to affect the
9285 subsequent behavior of floating-point arithmetic.
9287 Certain programming conventions support the intended model of use for the floating-
9289 <ul>
9290 <li> a function call does not alter its caller's floating-point control modes, clear its caller's
9291 floating-point status flags, nor depend on the state of its caller's floating-point status
9292 flags unless the function is so documented;
9293 <li> a function call is assumed to require default floating-point control modes, unless its
9294 documentation promises otherwise;
9295 <li> a function call is assumed to have the potential for raising floating-point exceptions,
9296 unless its documentation promises otherwise.
9297 </ul>
9299 The type
9300 <pre>
9301 fenv_t</pre>
9302 represents the entire floating-point environment.
9304 The type
9305 <pre>
9306 fexcept_t</pre>
9307 represents the floating-point status flags collectively, including any status the
9308 implementation associates with the flags.
9313 <!--page 200 -->
9315 Each of the macros
9316 <pre>
9317 FE_DIVBYZERO
9318 FE_INEXACT
9319 FE_INVALID
9320 FE_OVERFLOW
9321 FE_UNDERFLOW</pre>
9322 is defined if and only if the implementation supports the floating-point exception by
9323 means of the functions in 7.6.2.<sup><a href="#note181"><b>181)</b></a></sup> Additional implementation-defined floating-point
9324 exceptions, with macro definitions beginning with FE_ and an uppercase letter, may also
9325 be specified by the implementation. The defined macros expand to integer constant
9326 expressions with values such that bitwise ORs of all combinations of the macros result in
9327 distinct values, and furthermore, bitwise ANDs of all combinations of the macros result in
9330 The macro
9331 <pre>
9332 FE_ALL_EXCEPT</pre>
9333 is simply the bitwise OR of all floating-point exception macros defined by the
9334 implementation. If no such macros are defined, FE_ALL_EXCEPT shall be defined as 0.
9336 Each of the macros
9337 <pre>
9338 FE_DOWNWARD
9339 FE_TONEAREST
9340 FE_TOWARDZERO
9341 FE_UPWARD</pre>
9342 is defined if and only if the implementation supports getting and setting the represented
9343 rounding direction by means of the fegetround and fesetround functions.
9344 Additional implementation-defined rounding directions, with macro definitions beginning
9345 with FE_ and an uppercase letter, may also be specified by the implementation. The
9346 defined macros expand to integer constant expressions whose values are distinct
9349 The macro
9353 <!--page 201 -->
9354 <pre>
9355 FE_DFL_ENV</pre>
9356 represents the default floating-point environment -- the one installed at program startup
9357 <ul>
9358 <li> and has type ''pointer to const-qualified fenv_t''. It can be used as an argument to
9359 </ul>
9362 Additional implementation-defined environments, with macro definitions beginning with
9363 FE_ and an uppercase letter, and having type ''pointer to const-qualified fenv_t'', may
9364 also be specified by the implementation.
9367 <p><small><a name="note178" href="#note178">178)</a> This header is designed to support the floating-point exception status flags and directed-rounding
9368 control modes required by IEC 60559, and other similar floating-point state information. Also it is
9369 designed to facilitate code portability among all systems.
9370 </small>
9371 <p><small><a name="note179" href="#note179">179)</a> A floating-point status flag is not an object and can be set more than once within an expression.
9372 </small>
9373 <p><small><a name="note180" href="#note180">180)</a> With these conventions, a programmer can safely assume default floating-point control modes (or be
9374 unaware of them). The responsibilities associated with accessing the floating-point environment fall
9375 on the programmer or program that does so explicitly.
9376 </small>
9377 <p><small><a name="note181" href="#note181">181)</a> The implementation supports an exception if there are circumstances where a call to at least one of the
9378 functions in <a href="#7.6.2">7.6.2</a>, using the macro as the appropriate argument, will succeed. It is not necessary for
9379 all the functions to succeed all the time.
9380 </small>
9381 <p><small><a name="note182" href="#note182">182)</a> The macros should be distinct powers of two.
9382 </small>
9383 <p><small><a name="note183" href="#note183">183)</a> Even though the rounding direction macros may expand to constants corresponding to the values of
9384 FLT_ROUNDS, they are not required to do so.
9385 </small>
9390 <pre>
9392 #pragma STDC FENV_ACCESS on-off-switch</pre>
9395 The FENV_ACCESS pragma provides a means to inform the implementation when a
9396 program might access the floating-point environment to test floating-point status flags or
9397 run under non-default floating-point control modes.<sup><a href="#note184"><b>184)</b></a></sup> The pragma shall occur either
9398 outside external declarations or preceding all explicit declarations and statements inside a
9399 compound statement. When outside external declarations, the pragma takes effect from
9400 its occurrence until another FENV_ACCESS pragma is encountered, or until the end of
9401 the translation unit. When inside a compound statement, the pragma takes effect from its
9402 occurrence until another FENV_ACCESS pragma is encountered (including within a
9403 nested compound statement), or until the end of the compound statement; at the end of a
9404 compound statement the state for the pragma is restored to its condition just before the
9405 compound statement. If this pragma is used in any other context, the behavior is
9406 undefined. If part of a program tests floating-point status flags, sets floating-point control
9407 modes, or runs under non-default mode settings, but was translated with the state for the
9408 FENV_ACCESS pragma ''off'', the behavior is undefined. The default state (''on'' or
9409 ''off'') for the pragma is implementation-defined. (When execution passes from a part of
9410 the program translated with FENV_ACCESS ''off'' to a part translated with
9411 FENV_ACCESS ''on'', the state of the floating-point status flags is unspecified and the
9412 floating-point control modes have their default settings.)
9417 <!--page 202 -->
9419 EXAMPLE
9421 <pre>
9423 void f(double x)
9424 {
9425 #pragma STDC FENV_ACCESS ON
9426 void g(double);
9427 void h(double);
9428 /* ... */
9429 g(x + 1);
9430 h(x + 1);
9431 /* ... */
9432 }</pre>
9433 If the function g might depend on status flags set as a side effect of the first x + 1, or if the second
9434 x + 1 might depend on control modes set as a side effect of the call to function g, then the program shall
9435 contain an appropriately placed invocation of #pragma STDC FENV_ACCESS ON.<sup><a href="#note185"><b>185)</b></a></sup>
9439 <p><small><a name="note184" href="#note184">184)</a> The purpose of the FENV_ACCESS pragma is to allow certain optimizations that could subvert flag
9440 tests and mode changes (e.g., global common subexpression elimination, code motion, and constant
9441 folding). In general, if the state of FENV_ACCESS is ''off'', the translator can assume that default
9442 modes are in effect and the flags are not tested.
9443 </small>
9444 <p><small><a name="note185" href="#note185">185)</a> The side effects impose a temporal ordering that requires two evaluations of x + 1. On the other
9445 hand, without the #pragma STDC FENV_ACCESS ON pragma, and assuming the default state is
9446 ''off'', just one evaluation of x + 1 would suffice.
9447 </small>
9451 The following functions provide access to the floating-point status flags.<sup><a href="#note186"><b>186)</b></a></sup> The int
9452 input argument for the functions represents a subset of floating-point exceptions, and can
9453 be zero or the bitwise OR of one or more floating-point exception macros, for example
9454 FE_OVERFLOW | FE_INEXACT. For other argument values the behavior of these
9455 functions is undefined.
9458 <p><small><a name="note186" href="#note186">186)</a> The functions fetestexcept, feraiseexcept, and feclearexcept support the basic
9459 abstraction of flags that are either set or clear. An implementation may endow floating-point status
9460 flags with more information -- for example, the address of the code which first raised the floating-
9461 point exception; the functions fegetexceptflag and fesetexceptflag deal with the full
9462 content of flags.
9463 </small>
9468 <pre>
9470 int feclearexcept(int excepts);</pre>
9473 The feclearexcept function attempts to clear the supported floating-point exceptions
9474 represented by its argument.
9477 The feclearexcept function returns zero if the excepts argument is zero or if all
9478 the specified exceptions were successfully cleared. Otherwise, it returns a nonzero value.
9481 <!--page 203 -->
9486 <pre>
9488 int fegetexceptflag(fexcept_t *flagp,
9489 int excepts);</pre>
9492 The fegetexceptflag function attempts to store an implementation-defined
9493 representation of the states of the floating-point status flags indicated by the argument
9494 excepts in the object pointed to by the argument flagp.
9497 The fegetexceptflag function returns zero if the representation was successfully
9498 stored. Otherwise, it returns a nonzero value.
9503 <pre>
9505 int feraiseexcept(int excepts);</pre>
9508 The feraiseexcept function attempts to raise the supported floating-point exceptions
9509 represented by its argument.<sup><a href="#note187"><b>187)</b></a></sup> The order in which these floating-point exceptions are
9510 raised is unspecified, except as stated in <a href="#F.7.6">F.7.6</a>. Whether the feraiseexcept function
9511 additionally raises the ''inexact'' floating-point exception whenever it raises the
9512 ''overflow'' or ''underflow'' floating-point exception is implementation-defined.
9515 The feraiseexcept function returns zero if the excepts argument is zero or if all
9516 the specified exceptions were successfully raised. Otherwise, it returns a nonzero value.
9521 <!--page 204 -->
9524 <p><small><a name="note187" href="#note187">187)</a> The effect is intended to be similar to that of floating-point exceptions raised by arithmetic operations.
9525 Hence, enabled traps for floating-point exceptions raised by this function are taken. The specification
9527 </small>
9532 <pre>
9534 int fesetexceptflag(const fexcept_t *flagp,
9535 int excepts);</pre>
9538 The fesetexceptflag function attempts to set the floating-point status flags
9539 indicated by the argument excepts to the states stored in the object pointed to by
9540 flagp. The value of *flagp shall have been set by a previous call to
9541 fegetexceptflag whose second argument represented at least those floating-point
9542 exceptions represented by the argument excepts. This function does not raise floating-
9543 point exceptions, but only sets the state of the flags.
9546 The fesetexceptflag function returns zero if the excepts argument is zero or if
9547 all the specified flags were successfully set to the appropriate state. Otherwise, it returns
9548 a nonzero value.
9553 <pre>
9555 int fetestexcept(int excepts);</pre>
9558 The fetestexcept function determines which of a specified subset of the floating-
9559 point exception flags are currently set. The excepts argument specifies the floating-
9563 The fetestexcept function returns the value of the bitwise OR of the floating-point
9564 exception macros corresponding to the currently set floating-point exceptions included in
9565 excepts.
9567 EXAMPLE Call f if ''invalid'' is set, then g if ''overflow'' is set:
9572 <!--page 205 -->
9573 <pre>
9575 /* ... */
9576 {
9577 #pragma STDC FENV_ACCESS ON
9578 int set_excepts;
9579 feclearexcept(FE_INVALID | FE_OVERFLOW);
9580 // maybe raise exceptions
9581 set_excepts = fetestexcept(FE_INVALID | FE_OVERFLOW);
9582 if (set_excepts & FE_INVALID) f();
9583 if (set_excepts & FE_OVERFLOW) g();
9584 /* ... */
9585 }</pre>
9589 <p><small><a name="note188" href="#note188">188)</a> This mechanism allows testing several floating-point exceptions with just one function call.
9590 </small>
9594 The fegetround and fesetround functions provide control of rounding direction
9595 modes.
9600 <pre>
9602 int fegetround(void);</pre>
9605 The fegetround function gets the current rounding direction.
9608 The fegetround function returns the value of the rounding direction macro
9609 representing the current rounding direction or a negative value if there is no such
9610 rounding direction macro or the current rounding direction is not determinable.
9615 <pre>
9617 int fesetround(int round);</pre>
9620 The fesetround function establishes the rounding direction represented by its
9621 argument round. If the argument is not equal to the value of a rounding direction macro,
9622 the rounding direction is not changed.
9625 The fesetround function returns zero if and only if the requested rounding direction
9626 was established.
9627 <!--page 206 -->
9629 EXAMPLE Save, set, and restore the rounding direction. Report an error and abort if setting the
9630 rounding direction fails.
9631 <pre>
9634 void f(int round_dir)
9635 {
9636 #pragma STDC FENV_ACCESS ON
9637 int save_round;
9638 int setround_ok;
9639 save_round = fegetround();
9640 setround_ok = fesetround(round_dir);
9641 assert(setround_ok == 0);
9642 /* ... */
9643 fesetround(save_round);
9644 /* ... */
9645 }</pre>
9650 The functions in this section manage the floating-point environment -- status flags and
9651 control modes -- as one entity.
9656 <pre>
9658 int fegetenv(fenv_t *envp);</pre>
9661 The fegetenv function attempts to store the current floating-point environment in the
9662 object pointed to by envp.
9665 The fegetenv function returns zero if the environment was successfully stored.
9666 Otherwise, it returns a nonzero value.
9671 <pre>
9673 int feholdexcept(fenv_t *envp);</pre>
9676 The feholdexcept function saves the current floating-point environment in the object
9677 pointed to by envp, clears the floating-point status flags, and then installs a non-stop
9678 (continue on floating-point exceptions) mode, if available, for all floating-point
9680 <!--page 207 -->
9683 The feholdexcept function returns zero if and only if non-stop floating-point
9684 exception handling was successfully installed.
9687 <p><small><a name="note189" href="#note189">189)</a> IEC 60559 systems have a default non-stop mode, and typically at least one other mode for trap
9688 handling or aborting; if the system provides only the non-stop mode then installing it is trivial. For
9689 such systems, the feholdexcept function can be used in conjunction with the feupdateenv
9690 function to write routines that hide spurious floating-point exceptions from their callers.
9691 </small>
9696 <pre>
9698 int fesetenv(const fenv_t *envp);</pre>
9701 The fesetenv function attempts to establish the floating-point environment represented
9702 by the object pointed to by envp. The argument envp shall point to an object set by a
9703 call to fegetenv or feholdexcept, or equal a floating-point environment macro.
9704 Note that fesetenv merely installs the state of the floating-point status flags
9705 represented through its argument, and does not raise these floating-point exceptions.
9708 The fesetenv function returns zero if the environment was successfully established.
9709 Otherwise, it returns a nonzero value.
9714 <pre>
9716 int feupdateenv(const fenv_t *envp);</pre>
9719 The feupdateenv function attempts to save the currently raised floating-point
9720 exceptions in its automatic storage, install the floating-point environment represented by
9721 the object pointed to by envp, and then raise the saved floating-point exceptions. The
9722 argument envp shall point to an object set by a call to feholdexcept or fegetenv,
9723 or equal a floating-point environment macro.
9726 The feupdateenv function returns zero if all the actions were successfully carried out.
9727 Otherwise, it returns a nonzero value.
9732 <!--page 208 -->
9734 EXAMPLE Hide spurious underflow floating-point exceptions:
9735 <!--page 209 -->
9736 <pre>
9738 double f(double x)
9739 {
9740 #pragma STDC FENV_ACCESS ON
9741 double result;
9742 fenv_t save_env;
9743 if (feholdexcept(&save_env))
9744 return /* indication of an environmental problem */;
9745 // compute result
9746 if (/* test spurious underflow */)
9747 if (feclearexcept(FE_UNDERFLOW))
9748 return /* indication of an environmental problem */;
9749 if (feupdateenv(&save_env))
9750 return /* indication of an environmental problem */;
9751 return result;
9752 }</pre>
9756 The header <a href="#7.7"><float.h></a> defines several macros that expand to various limits and
9757 parameters of the standard floating-point types.
9759 The macros, their meanings, and the constraints (or restrictions) on their values are listed
9761 <!--page 210 -->
9765 The header <a href="#7.8"><inttypes.h></a> includes the header <a href="#7.18"><stdint.h></a> and extends it with
9766 additional facilities provided by hosted implementations.
9768 It declares functions for manipulating greatest-width integers and converting numeric
9769 character strings to greatest-width integers, and it declares the type
9770 <pre>
9771 imaxdiv_t</pre>
9772 which is a structure type that is the type of the value returned by the imaxdiv function.
9773 For each type declared in <a href="#7.18"><stdint.h></a>, it defines corresponding macros for conversion
9774 specifiers for use with the formatted input/output functions.<sup><a href="#note190"><b>190)</b></a></sup>
9775 <p><b> Forward references</b>: integer types <a href="#7.18"><stdint.h></a> (<a href="#7.18">7.18</a>), formatted input/output
9776 functions (<a href="#7.19.6">7.19.6</a>), formatted wide character input/output functions (<a href="#7.24.2">7.24.2</a>).
9779 <p><small><a name="note190" href="#note190">190)</a> See ''future library directions'' (<a href="#7.26.4">7.26.4</a>).
9780 </small>
9784 Each of the following object-like macros<sup><a href="#note191"><b>191)</b></a></sup> expands to a character string literal
9785 containing a conversion specifier, possibly modified by a length modifier, suitable for use
9786 within the format argument of a formatted input/output function when converting the
9787 corresponding integer type. These macro names have the general form of PRI (character
9788 string literals for the fprintf and fwprintf family) or SCN (character string literals
9789 for the fscanf and fwscanf family),<sup><a href="#note192"><b>192)</b></a></sup> followed by the conversion specifier,
9790 followed by a name corresponding to a similar type name in <a href="#7.18.1">7.18.1</a>. In these names, N
9791 represents the width of the type as described in <a href="#7.18.1">7.18.1</a>. For example, PRIdFAST32 can
9792 be used in a format string to print the value of an integer of type int_fast32_t.
9794 The fprintf macros for signed integers are:
9795 <pre>
9796 PRIdN PRIdLEASTN PRIdFASTN PRIdMAX PRIdPTR
9797 PRIiN PRIiLEASTN PRIiFASTN PRIiMAX PRIiPTR</pre>
9802 <!--page 211 -->
9804 The fprintf macros for unsigned integers are:
9806 <pre>
9807 PRIoN PRIoLEASTN PRIoFASTN PRIoMAX PRIoPTR
9808 PRIuN PRIuLEASTN PRIuFASTN PRIuMAX PRIuPTR
9809 PRIxN PRIxLEASTN PRIxFASTN PRIxMAX PRIxPTR
9810 PRIXN PRIXLEASTN PRIXFASTN PRIXMAX PRIXPTR</pre>
9811 The fscanf macros for signed integers are:
9813 <pre>
9814 SCNdN SCNdLEASTN SCNdFASTN SCNdMAX SCNdPTR
9815 SCNiN SCNiLEASTN SCNiFASTN SCNiMAX SCNiPTR</pre>
9816 The fscanf macros for unsigned integers are:
9818 <pre>
9819 SCNoN SCNoLEASTN SCNoFASTN SCNoMAX SCNoPTR
9820 SCNuN SCNuLEASTN SCNuFASTN SCNuMAX SCNuPTR
9821 SCNxN SCNxLEASTN SCNxFASTN SCNxMAX SCNxPTR</pre>
9822 For each type that the implementation provides in <a href="#7.18"><stdint.h></a>, the corresponding
9823 fprintf macros shall be defined and the corresponding fscanf macros shall be
9824 defined unless the implementation does not have a suitable fscanf length modifier for
9825 the type.
9827 EXAMPLE
9828 <pre>
9831 int main(void)
9832 {
9833 uintmax_t i = UINTMAX_MAX; // this type always exists
9834 wprintf(L"The largest integer value is %020"
9835 PRIxMAX "\n", i);
9836 return 0;
9837 }</pre>
9841 <p><small><a name="note191" href="#note191">191)</a> C++ implementations should define these macros only when __STDC_FORMAT_MACROS is defined
9843 </small>
9844 <p><small><a name="note192" href="#note192">192)</a> Separate macros are given for use with fprintf and fscanf functions because, in the general case,
9845 different format specifiers may be required for fprintf and fscanf, even when the type is the
9846 same.
9847 </small>
9854 <pre>
9856 intmax_t imaxabs(intmax_t j);</pre>
9859 The imaxabs function computes the absolute value of an integer j. If the result cannot
9864 <!--page 212 -->
9867 The imaxabs function returns the absolute value.
9870 <p><small><a name="note193" href="#note193">193)</a> The absolute value of the most negative number cannot be represented in two's complement.
9871 </small>
9876 <pre>
9878 imaxdiv_t imaxdiv(intmax_t numer, intmax_t denom);</pre>
9881 The imaxdiv function computes numer / denom and numer % denom in a single
9882 operation.
9885 The imaxdiv function returns a structure of type imaxdiv_t comprising both the
9886 quotient and the remainder. The structure shall contain (in either order) the members
9887 quot (the quotient) and rem (the remainder), each of which has type intmax_t. If
9888 either part of the result cannot be represented, the behavior is undefined.
9893 <pre>
9895 intmax_t strtoimax(const char * restrict nptr,
9896 char ** restrict endptr, int base);
9897 uintmax_t strtoumax(const char * restrict nptr,
9898 char ** restrict endptr, int base);</pre>
9901 The strtoimax and strtoumax functions are equivalent to the strtol, strtoll,
9902 strtoul, and strtoull functions, except that the initial portion of the string is
9903 converted to intmax_t and uintmax_t representation, respectively.
9906 The strtoimax and strtoumax functions return the converted value, if any. If no
9907 conversion could be performed, zero is returned. If the correct value is outside the range
9908 of representable values, INTMAX_MAX, INTMAX_MIN, or UINTMAX_MAX is returned
9909 (according to the return type and sign of the value, if any), and the value of the macro
9910 ERANGE is stored in errno.
9913 <!--page 213 -->
9918 <pre>
9921 intmax_t wcstoimax(const wchar_t * restrict nptr,
9922 wchar_t ** restrict endptr, int base);
9923 uintmax_t wcstoumax(const wchar_t * restrict nptr,
9924 wchar_t ** restrict endptr, int base);</pre>
9927 The wcstoimax and wcstoumax functions are equivalent to the wcstol, wcstoll,
9928 wcstoul, and wcstoull functions except that the initial portion of the wide string is
9929 converted to intmax_t and uintmax_t representation, respectively.
9932 The wcstoimax function returns the converted value, if any. If no conversion could be
9933 performed, zero is returned. If the correct value is outside the range of representable
9934 values, INTMAX_MAX, INTMAX_MIN, or UINTMAX_MAX is returned (according to the
9935 return type and sign of the value, if any), and the value of the macro ERANGE is stored in
9936 errno.
9939 <!--page 214 -->
9943 The header <a href="#7.9"><iso646.h></a> defines the following eleven macros (on the left) that expand
9944 to the corresponding tokens (on the right):
9945 <!--page 215 -->
9946 <pre>
9947 and &&
9948 and_eq &=
9949 bitand &
9950 bitor |
9951 compl ~
9952 not !
9953 not_eq !=
9954 or ||
9955 or_eq |=
9956 xor ^
9957 xor_eq ^=</pre>
9961 The header <a href="#7.10"><limits.h></a> defines several macros that expand to various limits and
9962 parameters of the standard integer types.
9964 The macros, their meanings, and the constraints (or restrictions) on their values are listed
9966 <!--page 216 -->
9970 The header <a href="#7.11"><locale.h></a> declares two functions, one type, and defines several macros.
9972 The type is
9973 <pre>
9974 struct lconv</pre>
9975 which contains members related to the formatting of numeric values. The structure shall
9976 contain at least the following members, in any order. The semantics of the members and
9977 their normal ranges are explained in <a href="#7.11.2.1">7.11.2.1</a>. In the "C" locale, the members shall have
9978 the values specified in the comments.
9979 <!--page 217 -->
9981 <pre>
9982 char *decimal_point; // "."
9983 char *thousands_sep; // ""
9984 char *grouping; // ""
9985 char *mon_decimal_point; // ""
9986 char *mon_thousands_sep; // ""
9987 char *mon_grouping; // ""
9988 char *positive_sign; // ""
9989 char *negative_sign; // ""
9990 char *currency_symbol; // ""
9991 char frac_digits; // CHAR_MAX
9992 char p_cs_precedes; // CHAR_MAX
9993 char n_cs_precedes; // CHAR_MAX
9994 char p_sep_by_space; // CHAR_MAX
9995 char n_sep_by_space; // CHAR_MAX
9996 char p_sign_posn; // CHAR_MAX
9997 char n_sign_posn; // CHAR_MAX
9998 char *int_curr_symbol; // ""
9999 char int_frac_digits; // CHAR_MAX
10000 char int_p_cs_precedes; // CHAR_MAX
10001 char int_n_cs_precedes; // CHAR_MAX
10002 char int_p_sep_by_space; // CHAR_MAX
10003 char int_n_sep_by_space; // CHAR_MAX
10004 char int_p_sign_posn; // CHAR_MAX
10005 char int_n_sign_posn; // CHAR_MAX</pre>
10007 <pre>
10008 LC_ALL
10009 LC_COLLATE
10010 LC_CTYPE
10011 LC_MONETARY
10012 LC_NUMERIC
10013 LC_TIME</pre>
10014 which expand to integer constant expressions with distinct values, suitable for use as the
10015 first argument to the setlocale function.<sup><a href="#note194"><b>194)</b></a></sup> Additional macro definitions, beginning
10016 with the characters LC_ and an uppercase letter,<sup><a href="#note195"><b>195)</b></a></sup> may also be specified by the
10017 implementation.
10020 <p><small><a name="note194" href="#note194">194)</a> ISO/IEC 9945-2 specifies locale and charmap formats that may be used to specify locales for C.
10021 </small>
10022 <p><small><a name="note195" href="#note195">195)</a> See ''future library directions'' (<a href="#7.26.5">7.26.5</a>).
10023 </small>
10030 <pre>
10032 char *setlocale(int category, const char *locale);</pre>
10035 The setlocale function selects the appropriate portion of the program's locale as
10036 specified by the category and locale arguments. The setlocale function may be
10037 used to change or query the program's entire current locale or portions thereof. The value
10038 LC_ALL for category names the program's entire locale; the other values for
10039 category name only a portion of the program's locale. LC_COLLATE affects the
10040 behavior of the strcoll and strxfrm functions. LC_CTYPE affects the behavior of
10041 the character handling functions<sup><a href="#note196"><b>196)</b></a></sup> and the multibyte and wide character functions.
10042 LC_MONETARY affects the monetary formatting information returned by the
10043 localeconv function. LC_NUMERIC affects the decimal-point character for the
10044 formatted input/output functions and the string conversion functions, as well as the
10045 nonmonetary formatting information returned by the localeconv function. LC_TIME
10046 affects the behavior of the strftime and wcsftime functions.
10048 A value of "C" for locale specifies the minimal environment for C translation; a value
10049 of "" for locale specifies the locale-specific native environment. Other
10050 implementation-defined strings may be passed as the second argument to setlocale.
10052 <!--page 218 -->
10054 At program startup, the equivalent of
10055 <pre>
10057 is executed.
10059 The implementation shall behave as if no library function calls the setlocale function.
10062 If a pointer to a string is given for locale and the selection can be honored, the
10063 setlocale function returns a pointer to the string associated with the specified
10064 category for the new locale. If the selection cannot be honored, the setlocale
10065 function returns a null pointer and the program's locale is not changed.
10067 A null pointer for locale causes the setlocale function to return a pointer to the
10068 string associated with the category for the program's current locale; the program's
10071 The pointer to string returned by the setlocale function is such that a subsequent call
10072 with that string value and its associated category will restore that part of the program's
10073 locale. The string pointed to shall not be modified by the program, but may be
10074 overwritten by a subsequent call to the setlocale function.
10075 <p><b> Forward references</b>: formatted input/output functions (<a href="#7.19.6">7.19.6</a>), multibyte/wide
10076 character conversion functions (<a href="#7.20.7">7.20.7</a>), multibyte/wide string conversion functions
10077 (<a href="#7.20.8">7.20.8</a>), numeric conversion functions (<a href="#7.20.1">7.20.1</a>), the strcoll function (<a href="#7.21.4.3">7.21.4.3</a>), the
10078 strftime function (<a href="#7.23.3.5">7.23.3.5</a>), the strxfrm function (<a href="#7.21.4.5">7.21.4.5</a>).
10081 <p><small><a name="note196" href="#note196">196)</a> The only functions in <a href="#7.4">7.4</a> whose behavior is not affected by the current locale are isdigit and
10082 isxdigit.
10083 </small>
10084 <p><small><a name="note197" href="#note197">197)</a> The implementation shall arrange to encode in a string the various categories due to a heterogeneous
10085 locale when category has the value LC_ALL.
10086 </small>
10093 <pre>
10095 struct lconv *localeconv(void);</pre>
10098 The localeconv function sets the components of an object with type struct lconv
10099 with values appropriate for the formatting of numeric quantities (monetary and otherwise)
10100 according to the rules of the current locale.
10102 The members of the structure with type char * are pointers to strings, any of which
10103 (except decimal_point) can point to "", to indicate that the value is not available in
10104 the current locale or is of zero length. Apart from grouping and mon_grouping, the
10106 <!--page 219 -->
10107 strings shall start and end in the initial shift state. The members with type char are
10108 nonnegative numbers, any of which can be CHAR_MAX to indicate that the value is not
10109 available in the current locale. The members include the following:
10110 char *decimal_point
10111 <pre>
10112 The decimal-point character used to format nonmonetary quantities.</pre>
10113 char *thousands_sep
10114 <pre>
10115 The character used to separate groups of digits before the decimal-point
10116 character in formatted nonmonetary quantities.</pre>
10117 char *grouping
10118 <pre>
10119 A string whose elements indicate the size of each group of digits in
10120 formatted nonmonetary quantities.</pre>
10121 char *mon_decimal_point
10122 <pre>
10123 The decimal-point used to format monetary quantities.</pre>
10124 char *mon_thousands_sep
10125 <pre>
10126 The separator for groups of digits before the decimal-point in formatted
10127 monetary quantities.</pre>
10128 char *mon_grouping
10129 <pre>
10130 A string whose elements indicate the size of each group of digits in
10131 formatted monetary quantities.</pre>
10132 char *positive_sign
10133 <pre>
10134 The string used to indicate a nonnegative-valued formatted monetary
10135 quantity.</pre>
10136 char *negative_sign
10137 <pre>
10138 The string used to indicate a negative-valued formatted monetary quantity.</pre>
10139 char *currency_symbol
10140 <pre>
10141 The local currency symbol applicable to the current locale.</pre>
10142 char frac_digits
10143 <pre>
10144 The number of fractional digits (those after the decimal-point) to be
10145 displayed in a locally formatted monetary quantity.</pre>
10146 char p_cs_precedes
10147 <pre>
10149 succeeds the value for a nonnegative locally formatted monetary quantity.</pre>
10150 char n_cs_precedes
10151 <!--page 220 -->
10152 <pre>
10154 succeeds the value for a negative locally formatted monetary quantity.</pre>
10155 char p_sep_by_space
10156 <pre>
10157 Set to a value indicating the separation of the currency_symbol, the
10158 sign string, and the value for a nonnegative locally formatted monetary
10159 quantity.</pre>
10160 char n_sep_by_space
10161 <pre>
10162 Set to a value indicating the separation of the currency_symbol, the
10163 sign string, and the value for a negative locally formatted monetary
10164 quantity.</pre>
10165 char p_sign_posn
10166 <pre>
10167 Set to a value indicating the positioning of the positive_sign for a
10168 nonnegative locally formatted monetary quantity.</pre>
10169 char n_sign_posn
10170 <pre>
10171 Set to a value indicating the positioning of the negative_sign for a
10172 negative locally formatted monetary quantity.</pre>
10173 char *int_curr_symbol
10174 <pre>
10175 The international currency symbol applicable to the current locale. The
10176 first three characters contain the alphabetic international currency symbol
10177 in accordance with those specified in ISO 4217. The fourth character
10178 (immediately preceding the null character) is the character used to separate
10179 the international currency symbol from the monetary quantity.</pre>
10180 char int_frac_digits
10181 <pre>
10182 The number of fractional digits (those after the decimal-point) to be
10183 displayed in an internationally formatted monetary quantity.</pre>
10184 char int_p_cs_precedes
10185 <pre>
10187 succeeds the value for a nonnegative internationally formatted monetary
10188 quantity.</pre>
10189 char int_n_cs_precedes
10190 <pre>
10192 succeeds the value for a negative internationally formatted monetary
10193 quantity.</pre>
10194 char int_p_sep_by_space
10195 <!--page 221 -->
10196 <pre>
10197 Set to a value indicating the separation of the int_curr_symbol, the
10198 sign string, and the value for a nonnegative internationally formatted
10199 monetary quantity.</pre>
10200 char int_n_sep_by_space
10201 <pre>
10202 Set to a value indicating the separation of the int_curr_symbol, the
10203 sign string, and the value for a negative internationally formatted monetary
10204 quantity.</pre>
10205 char int_p_sign_posn
10206 <pre>
10207 Set to a value indicating the positioning of the positive_sign for a
10208 nonnegative internationally formatted monetary quantity.</pre>
10209 char int_n_sign_posn
10211 <pre>
10212 Set to a value indicating the positioning of the negative_sign for a
10213 negative internationally formatted monetary quantity.</pre>
10214 The elements of grouping and mon_grouping are interpreted according to the
10215 following:
10216 CHAR_MAX No further grouping is to be performed.
10217 0 The previous element is to be repeatedly used for the remainder of the
10218 <pre>
10219 digits.</pre>
10220 other The integer value is the number of digits that compose the current group.
10222 <pre>
10223 The next element is examined to determine the size of the next group of
10224 digits before the current group.</pre>
10225 The values of p_sep_by_space, n_sep_by_space, int_p_sep_by_space,
10226 and int_n_sep_by_space are interpreted according to the following:
10227 0 No space separates the currency symbol and value.
10228 1 If the currency symbol and sign string are adjacent, a space separates them from the
10229 <pre>
10230 value; otherwise, a space separates the currency symbol from the value.</pre>
10231 2 If the currency symbol and sign string are adjacent, a space separates them;
10232 <pre>
10233 otherwise, a space separates the sign string from the value.</pre>
10234 For int_p_sep_by_space and int_n_sep_by_space, the fourth character of
10235 int_curr_symbol is used instead of a space.
10237 The values of p_sign_posn, n_sign_posn, int_p_sign_posn, and
10238 int_n_sign_posn are interpreted according to the following:
10239 0 Parentheses surround the quantity and currency symbol.
10240 1 The sign string precedes the quantity and currency symbol.
10241 2 The sign string succeeds the quantity and currency symbol.
10242 3 The sign string immediately precedes the currency symbol.
10243 4 The sign string immediately succeeds the currency symbol.
10244 <!--page 222 -->
10246 The implementation shall behave as if no library function calls the localeconv
10247 function.
10250 The localeconv function returns a pointer to the filled-in object. The structure
10251 pointed to by the return value shall not be modified by the program, but may be
10252 overwritten by a subsequent call to the localeconv function. In addition, calls to the
10253 setlocale function with categories LC_ALL, LC_MONETARY, or LC_NUMERIC may
10254 overwrite the contents of the structure.
10256 EXAMPLE 1 The following table illustrates rules which may well be used by four countries to format
10257 monetary quantities.
10258 <pre>
10259 Local format International format</pre>
10261 Country Positive Negative Positive Negative
10268 For these four countries, the respective values for the monetary members of the structure returned by
10269 localeconv could be:
10270 <pre>
10271 Country1 Country2 Country3 Country4</pre>
10279 frac_digits 2 0 2 2
10280 p_cs_precedes 0 1 1 1
10281 n_cs_precedes 0 1 1 1
10282 p_sep_by_space 1 0 1 0
10283 n_sep_by_space 1 0 2 0
10284 p_sign_posn 1 1 1 1
10285 n_sign_posn 1 1 4 2
10287 int_frac_digits 2 0 2 2
10288 int_p_cs_precedes 1 1 1 1
10289 int_n_cs_precedes 1 1 1 1
10290 int_p_sep_by_space 1 1 1 1
10291 int_n_sep_by_space 2 1 2 1
10292 int_p_sign_posn 1 1 1 1
10293 int_n_sign_posn 4 1 4 2
10294 <!--page 223 -->
10296 EXAMPLE 2 The following table illustrates how the cs_precedes, sep_by_space, and sign_posn members
10297 affect the formatted value.
10298 <pre>
10299 p_sep_by_space</pre>
10301 p_cs_precedes p_sign_posn 0 1 2
10303 <pre>
10310 <!--page 224 -->
10311 <pre>
10320 The header <a href="#7.12"><math.h></a> declares two types and many mathematical functions and defines
10321 several macros. Most synopses specify a family of functions consisting of a principal
10322 function with one or more double parameters, a double return value, or both; and
10323 other functions with the same name but with f and l suffixes, which are corresponding
10324 functions with float and long double parameters, return values, or both.<sup><a href="#note198"><b>198)</b></a></sup>
10325 Integer arithmetic functions and conversion functions are discussed later.
10327 The types
10328 <pre>
10329 float_t
10330 double_t</pre>
10331 are floating types at least as wide as float and double, respectively, and such that
10332 double_t is at least as wide as float_t. If FLT_EVAL_METHOD equals 0,
10333 float_t and double_t are float and double, respectively; if
10334 FLT_EVAL_METHOD equals 1, they are both double; if FLT_EVAL_METHOD equals
10335 2, they are both long double; and for other values of FLT_EVAL_METHOD, they are
10338 The macro
10339 <pre>
10340 HUGE_VAL</pre>
10341 expands to a positive double constant expression, not necessarily representable as a
10342 float. The macros
10343 <pre>
10344 HUGE_VALF
10345 HUGE_VALL</pre>
10346 are respectively float and long double analogs of HUGE_VAL.<sup><a href="#note200"><b>200)</b></a></sup>
10348 The macro
10349 <pre>
10350 INFINITY</pre>
10351 expands to a constant expression of type float representing positive or unsigned
10352 infinity, if available; else to a positive constant of type float that overflows at
10356 <!--page 225 -->
10359 The macro
10360 <pre>
10361 NAN</pre>
10362 is defined if and only if the implementation supports quiet NaNs for the float type. It
10363 expands to a constant expression of type float representing a quiet NaN.
10365 The number classification macros
10366 <pre>
10367 FP_INFINITE
10368 FP_NAN
10369 FP_NORMAL
10370 FP_SUBNORMAL
10371 FP_ZERO</pre>
10372 represent the mutually exclusive kinds of floating-point values. They expand to integer
10373 constant expressions with distinct values. Additional implementation-defined floating-
10374 point classifications, with macro definitions beginning with FP_ and an uppercase letter,
10375 may also be specified by the implementation.
10377 The macro
10378 <pre>
10379 FP_FAST_FMA</pre>
10380 is optionally defined. If defined, it indicates that the fma function generally executes
10381 about as fast as, or faster than, a multiply and an add of double operands.<sup><a href="#note202"><b>202)</b></a></sup> The
10382 macros
10383 <pre>
10384 FP_FAST_FMAF
10385 FP_FAST_FMAL</pre>
10386 are, respectively, float and long double analogs of FP_FAST_FMA. If defined,
10387 these macros expand to the integer constant 1.
10389 The macros
10390 <pre>
10391 FP_ILOGB0
10392 FP_ILOGBNAN</pre>
10393 expand to integer constant expressions whose values are returned by ilogb(x) if x is
10394 zero or NaN, respectively. The value of FP_ILOGB0 shall be either INT_MIN or
10395 -INT_MAX. The value of FP_ILOGBNAN shall be either INT_MAX or INT_MIN.
10398 <!--page 226 -->
10400 The macros
10401 <pre>
10402 MATH_ERRNO
10403 MATH_ERREXCEPT</pre>
10405 <pre>
10406 math_errhandling</pre>
10407 expands to an expression that has type int and the value MATH_ERRNO,
10408 MATH_ERREXCEPT, or the bitwise OR of both. The value of math_errhandling is
10409 constant for the duration of the program. It is unspecified whether
10410 math_errhandling is a macro or an identifier with external linkage. If a macro
10411 definition is suppressed or a program defines an identifier with the name
10412 math_errhandling, the behavior is undefined. If the expression
10413 math_errhandling & MATH_ERREXCEPT can be nonzero, the implementation
10414 shall define the macros FE_DIVBYZERO, FE_INVALID, and FE_OVERFLOW in
10418 <p><small><a name="note198" href="#note198">198)</a> Particularly on systems with wide expression evaluation, a <a href="#7.12"><math.h></a> function might pass arguments
10419 and return values in wider format than the synopsis prototype indicates.
10420 </small>
10421 <p><small><a name="note199" href="#note199">199)</a> The types float_t and double_t are intended to be the implementation's most efficient types at
10423 type float_t is the narrowest type used by the implementation to evaluate floating expressions.
10424 </small>
10425 <p><small><a name="note200" href="#note200">200)</a> HUGE_VAL, HUGE_VALF, and HUGE_VALL can be positive infinities in an implementation that
10426 supports infinities.
10427 </small>
10428 <p><small><a name="note201" href="#note201">201)</a> In this case, using INFINITY will violate the constraint in <a href="#6.4.4">6.4.4</a> and thus require a diagnostic.
10429 </small>
10430 <p><small><a name="note202" href="#note202">202)</a> Typically, the FP_FAST_FMA macro is defined if and only if the fma function is implemented
10431 directly with a hardware multiply-add instruction. Software implementations are expected to be
10432 substantially slower.
10433 </small>
10437 The behavior of each of the functions in <a href="#7.12"><math.h></a> is specified for all representable
10438 values of its input arguments, except where stated otherwise. Each function shall execute
10439 as if it were a single operation without generating any externally visible exceptional
10440 conditions.
10442 For all functions, a domain error occurs if an input argument is outside the domain over
10443 which the mathematical function is defined. The description of each function lists any
10444 required domain errors; an implementation may define additional domain errors, provided
10445 that such errors are consistent with the mathematical definition of the function.<sup><a href="#note203"><b>203)</b></a></sup> On a
10446 domain error, the function returns an implementation-defined value; if the integer
10447 expression math_errhandling & MATH_ERRNO is nonzero, the integer expression
10448 errno acquires the value EDOM; if the integer expression math_errhandling &
10449 MATH_ERREXCEPT is nonzero, the ''invalid'' floating-point exception is raised.
10451 Similarly, a range error occurs if the mathematical result of the function cannot be
10452 represented in an object of the specified type, due to extreme magnitude.
10454 A floating result overflows if the magnitude of the mathematical result is finite but so
10455 large that the mathematical result cannot be represented without extraordinary roundoff
10456 error in an object of the specified type. If a floating result overflows and default rounding
10457 is in effect, or if the mathematical result is an exact infinity from finite arguments (for
10458 example log(0.0)), then the function returns the value of the macro HUGE_VAL,
10461 <!--page 227 -->
10462 HUGE_VALF, or HUGE_VALL according to the return type, with the same sign as the
10463 correct value of the function; if the integer expression math_errhandling &
10464 MATH_ERRNO is nonzero, the integer expression errno acquires the value ERANGE; if
10465 the integer expression math_errhandling & MATH_ERREXCEPT is nonzero, the
10466 ''divide-by-zero'' floating-point exception is raised if the mathematical result is an exact
10467 infinity and the ''overflow'' floating-point exception is raised otherwise.
10469 The result underflows if the magnitude of the mathematical result is so small that the
10470 mathematical result cannot be represented, without extraordinary roundoff error, in an
10471 object of the specified type.<sup><a href="#note204"><b>204)</b></a></sup> If the result underflows, the function returns an
10472 implementation-defined value whose magnitude is no greater than the smallest
10473 normalized positive number in the specified type; if the integer expression
10474 math_errhandling & MATH_ERRNO is nonzero, whether errno acquires the
10475 value ERANGE is implementation-defined; if the integer expression
10476 math_errhandling & MATH_ERREXCEPT is nonzero, whether the ''underflow''
10477 floating-point exception is raised is implementation-defined.
10480 <p><small><a name="note203" href="#note203">203)</a> In an implementation that supports infinities, this allows an infinity as an argument to be a domain
10481 error if the mathematical domain of the function does not include the infinity.
10482 </small>
10483 <p><small><a name="note204" href="#note204">204)</a> The term underflow here is intended to encompass both ''gradual underflow'' as in IEC 60559 and
10484 also ''flush-to-zero'' underflow.
10485 </small>
10490 <pre>
10492 #pragma STDC FP_CONTRACT on-off-switch</pre>
10495 The FP_CONTRACT pragma can be used to allow (if the state is ''on'') or disallow (if the
10496 state is ''off'') the implementation to contract expressions (<a href="#6.5">6.5</a>). Each pragma can occur
10497 either outside external declarations or preceding all explicit declarations and statements
10498 inside a compound statement. When outside external declarations, the pragma takes
10499 effect from its occurrence until another FP_CONTRACT pragma is encountered, or until
10500 the end of the translation unit. When inside a compound statement, the pragma takes
10501 effect from its occurrence until another FP_CONTRACT pragma is encountered
10502 (including within a nested compound statement), or until the end of the compound
10503 statement; at the end of a compound statement the state for the pragma is restored to its
10504 condition just before the compound statement. If this pragma is used in any other
10505 context, the behavior is undefined. The default state (''on'' or ''off'') for the pragma is
10506 implementation-defined.
10511 <!--page 228 -->
10515 In the synopses in this subclause, real-floating indicates that the argument shall be an
10516 expression of real floating type.
10521 <pre>
10523 int fpclassify(real-floating x);</pre>
10526 The fpclassify macro classifies its argument value as NaN, infinite, normal,
10527 subnormal, zero, or into another implementation-defined category. First, an argument
10528 represented in a format wider than its semantic type is converted to its semantic type.
10529 Then classification is based on the type of the argument.<sup><a href="#note205"><b>205)</b></a></sup>
10532 The fpclassify macro returns the value of the number classification macro
10533 appropriate to the value of its argument.
10535 EXAMPLE The fpclassify macro might be implemented in terms of ordinary functions as
10536 <pre>
10537 #define fpclassify(x) \
10538 ((sizeof (x) == sizeof (float)) ? __fpclassifyf(x) : \
10539 (sizeof (x) == sizeof (double)) ? __fpclassifyd(x) : \
10540 __fpclassifyl(x))</pre>
10544 <p><small><a name="note205" href="#note205">205)</a> Since an expression can be evaluated with more range and precision than its type has, it is important to
10545 know the type that classification is based on. For example, a normal long double value might
10546 become subnormal when converted to double, and zero when converted to float.
10547 </small>
10552 <pre>
10554 int isfinite(real-floating x);</pre>
10557 The isfinite macro determines whether its argument has a finite value (zero,
10558 subnormal, or normal, and not infinite or NaN). First, an argument represented in a
10559 format wider than its semantic type is converted to its semantic type. Then determination
10560 is based on the type of the argument.
10565 <!--page 229 -->
10568 The isfinite macro returns a nonzero value if and only if its argument has a finite
10569 value.
10574 <pre>
10576 int isinf(real-floating x);</pre>
10579 The isinf macro determines whether its argument value is an infinity (positive or
10580 negative). First, an argument represented in a format wider than its semantic type is
10581 converted to its semantic type. Then determination is based on the type of the argument.
10584 The isinf macro returns a nonzero value if and only if its argument has an infinite
10585 value.
10590 <pre>
10592 int isnan(real-floating x);</pre>
10595 The isnan macro determines whether its argument value is a NaN. First, an argument
10596 represented in a format wider than its semantic type is converted to its semantic type.
10597 Then determination is based on the type of the argument.<sup><a href="#note206"><b>206)</b></a></sup>
10600 The isnan macro returns a nonzero value if and only if its argument has a NaN value.
10603 <p><small><a name="note206" href="#note206">206)</a> For the isnan macro, the type for determination does not matter unless the implementation supports
10604 NaNs in the evaluation type but not in the semantic type.
10605 </small>
10610 <pre>
10612 int isnormal(real-floating x);</pre>
10617 <!--page 230 -->
10620 The isnormal macro determines whether its argument value is normal (neither zero,
10621 subnormal, infinite, nor NaN). First, an argument represented in a format wider than its
10622 semantic type is converted to its semantic type. Then determination is based on the type
10623 of the argument.
10626 The isnormal macro returns a nonzero value if and only if its argument has a normal
10627 value.
10632 <pre>
10634 int signbit(real-floating x);</pre>
10637 The signbit macro determines whether the sign of its argument value is negative.<sup><a href="#note207"><b>207)</b></a></sup>
10640 The signbit macro returns a nonzero value if and only if the sign of its argument value
10641 is negative.
10644 <p><small><a name="note207" href="#note207">207)</a> The signbit macro reports the sign of all values, including infinities, zeros, and NaNs. If zero is
10645 unsigned, it is treated as positive.
10646 </small>
10653 <pre>
10655 double acos(double x);
10656 float acosf(float x);
10657 long double acosl(long double x);</pre>
10660 The acos functions compute the principal value of the arc cosine of x. A domain error
10664 The acos functions return arccos x in the interval [0, pi ] radians.
10669 <!--page 231 -->
10674 <pre>
10676 double asin(double x);
10677 float asinf(float x);
10678 long double asinl(long double x);</pre>
10681 The asin functions compute the principal value of the arc sine of x. A domain error
10690 <pre>
10692 double atan(double x);
10693 float atanf(float x);
10694 long double atanl(long double x);</pre>
10697 The atan functions compute the principal value of the arc tangent of x.
10705 <pre>
10707 double atan2(double y, double x);
10708 float atan2f(float y, float x);
10709 long double atan2l(long double y, long double x);</pre>
10712 The atan2 functions compute the value of the arc tangent of y/x, using the signs of both
10713 arguments to determine the quadrant of the return value. A domain error may occur if
10714 both arguments are zero.
10717 The atan2 functions return arctan y/x in the interval [-pi , +pi ] radians.
10718 <!--page 232 -->
10723 <pre>
10725 double cos(double x);
10726 float cosf(float x);
10727 long double cosl(long double x);</pre>
10730 The cos functions compute the cosine of x (measured in radians).
10733 The cos functions return cos x.
10738 <pre>
10740 double sin(double x);
10741 float sinf(float x);
10742 long double sinl(long double x);</pre>
10745 The sin functions compute the sine of x (measured in radians).
10748 The sin functions return sin x.
10753 <pre>
10755 double tan(double x);
10756 float tanf(float x);
10757 long double tanl(long double x);</pre>
10760 The tan functions return the tangent of x (measured in radians).
10763 The tan functions return tan x.
10764 <!--page 233 -->
10771 <pre>
10773 double acosh(double x);
10774 float acoshf(float x);
10775 long double acoshl(long double x);</pre>
10778 The acosh functions compute the (nonnegative) arc hyperbolic cosine of x. A domain
10779 error occurs for arguments less than 1.
10782 The acosh functions return arcosh x in the interval [0, +(inf)].
10787 <pre>
10789 double asinh(double x);
10790 float asinhf(float x);
10791 long double asinhl(long double x);</pre>
10794 The asinh functions compute the arc hyperbolic sine of x.
10797 The asinh functions return arsinh x.
10802 <pre>
10804 double atanh(double x);
10805 float atanhf(float x);
10806 long double atanhl(long double x);</pre>
10809 The atanh functions compute the arc hyperbolic tangent of x. A domain error occurs
10812 <!--page 234 -->
10815 The atanh functions return artanh x.
10820 <pre>
10822 double cosh(double x);
10823 float coshf(float x);
10824 long double coshl(long double x);</pre>
10827 The cosh functions compute the hyperbolic cosine of x. A range error occurs if the
10828 magnitude of x is too large.
10831 The cosh functions return cosh x.
10836 <pre>
10838 double sinh(double x);
10839 float sinhf(float x);
10840 long double sinhl(long double x);</pre>
10843 The sinh functions compute the hyperbolic sine of x. A range error occurs if the
10844 magnitude of x is too large.
10847 The sinh functions return sinh x.
10852 <pre>
10854 double tanh(double x);
10855 float tanhf(float x);
10856 long double tanhl(long double x);</pre>
10859 The tanh functions compute the hyperbolic tangent of x.
10860 <!--page 235 -->
10863 The tanh functions return tanh x.
10870 <pre>
10872 double exp(double x);
10873 float expf(float x);
10874 long double expl(long double x);</pre>
10877 The exp functions compute the base-e exponential of x. A range error occurs if the
10878 magnitude of x is too large.
10881 The exp functions return ex .
10886 <pre>
10888 double exp2(double x);
10889 float exp2f(float x);
10890 long double exp2l(long double x);</pre>
10893 The exp2 functions compute the base-2 exponential of x. A range error occurs if the
10894 magnitude of x is too large.
10897 The exp2 functions return 2x .
10902 <!--page 236 -->
10903 <pre>
10905 double expm1(double x);
10906 float expm1f(float x);
10907 long double expm1l(long double x);</pre>
10910 The expm1 functions compute the base-e exponential of the argument, minus 1. A range
10914 The expm1 functions return ex - 1.
10917 <p><small><a name="note208" href="#note208">208)</a> For small magnitude x, expm1(x) is expected to be more accurate than exp(x) - 1.
10918 </small>
10923 <pre>
10925 double frexp(double value, int *exp);
10926 float frexpf(float value, int *exp);
10927 long double frexpl(long double value, int *exp);</pre>
10930 The frexp functions break a floating-point number into a normalized fraction and an
10931 integral power of 2. They store the integer in the int object pointed to by exp.
10934 If value is not a floating-point number, the results are unspecified. Otherwise, the
10936 zero, and value equals x x 2*exp . If value is zero, both parts of the result are zero.
10941 <pre>
10943 int ilogb(double x);
10944 int ilogbf(float x);
10945 int ilogbl(long double x);</pre>
10948 The ilogb functions extract the exponent of x as a signed int value. If x is zero they
10949 compute the value FP_ILOGB0; if x is infinite they compute the value INT_MAX; if x is
10950 a NaN they compute the value FP_ILOGBNAN; otherwise, they are equivalent to calling
10951 the corresponding logb function and casting the returned value to type int. A domain
10952 error or range error may occur if x is zero, infinite, or NaN. If the correct value is outside
10953 the range of the return type, the numeric result is unspecified.
10958 <!--page 237 -->
10961 The ilogb functions return the exponent of x as a signed int value.
10967 <pre>
10969 double ldexp(double x, int exp);
10970 float ldexpf(float x, int exp);
10971 long double ldexpl(long double x, int exp);</pre>
10974 The ldexp functions multiply a floating-point number by an integral power of 2. A
10975 range error may occur.
10978 The ldexp functions return x x 2exp .
10983 <pre>
10985 double log(double x);
10986 float logf(float x);
10987 long double logl(long double x);</pre>
10990 The log functions compute the base-e (natural) logarithm of x. A domain error occurs if
10991 the argument is negative. A range error may occur if the argument is zero.
10994 The log functions return loge x.
10999 <!--page 238 -->
11000 <pre>
11002 double log10(double x);
11003 float log10f(float x);
11004 long double log10l(long double x);</pre>
11007 The log10 functions compute the base-10 (common) logarithm of x. A domain error
11008 occurs if the argument is negative. A range error may occur if the argument is zero.
11011 The log10 functions return log10 x.
11016 <pre>
11018 double log1p(double x);
11019 float log1pf(float x);
11020 long double log1pl(long double x);</pre>
11023 The log1p functions compute the base-e (natural) logarithm of 1 plus the argument.<sup><a href="#note209"><b>209)</b></a></sup>
11024 A domain error occurs if the argument is less than -1. A range error may occur if the
11025 argument equals -1.
11028 The log1p functions return loge (1 + x).
11031 <p><small><a name="note209" href="#note209">209)</a> For small magnitude x, log1p(x) is expected to be more accurate than log(1 + x).
11032 </small>
11037 <pre>
11039 double log2(double x);
11040 float log2f(float x);
11041 long double log2l(long double x);</pre>
11044 The log2 functions compute the base-2 logarithm of x. A domain error occurs if the
11045 argument is less than zero. A range error may occur if the argument is zero.
11048 The log2 functions return log2 x.
11053 <!--page 239 -->
11058 <pre>
11060 double logb(double x);
11061 float logbf(float x);
11062 long double logbl(long double x);</pre>
11065 The logb functions extract the exponent of x, as a signed integer value in floating-point
11066 format. If x is subnormal it is treated as though it were normalized; thus, for positive
11067 finite x,
11068 <pre>
11070 A domain error or range error may occur if the argument is zero.
11073 The logb functions return the signed exponent of x.
11078 <pre>
11080 double modf(double value, double *iptr);
11081 float modff(float value, float *iptr);
11082 long double modfl(long double value, long double *iptr);</pre>
11085 The modf functions break the argument value into integral and fractional parts, each of
11086 which has the same type and sign as the argument. They store the integral part (in
11087 floating-point format) in the object pointed to by iptr.
11090 The modf functions return the signed fractional part of value.
11091 <!--page 240 -->
11096 <pre>
11098 double scalbn(double x, int n);
11099 float scalbnf(float x, int n);
11100 long double scalbnl(long double x, int n);
11101 double scalbln(double x, long int n);
11102 float scalblnf(float x, long int n);
11103 long double scalblnl(long double x, long int n);</pre>
11106 The scalbn and scalbln functions compute x x FLT_RADIXn efficiently, not
11107 normally by computing FLT_RADIXn explicitly. A range error may occur.
11110 The scalbn and scalbln functions return x x FLT_RADIXn .
11117 <pre>
11119 double cbrt(double x);
11120 float cbrtf(float x);
11121 long double cbrtl(long double x);</pre>
11124 The cbrt functions compute the real cube root of x.
11127 The cbrt functions return x1/3 .
11132 <pre>
11134 double fabs(double x);
11135 float fabsf(float x);
11136 long double fabsl(long double x);</pre>
11139 The fabs functions compute the absolute value of a floating-point number x.
11140 <!--page 241 -->
11143 The fabs functions return | x |.
11148 <pre>
11150 double hypot(double x, double y);
11151 float hypotf(float x, float y);
11152 long double hypotl(long double x, long double y);</pre>
11155 The hypot functions compute the square root of the sum of the squares of x and y,
11156 without undue overflow or underflow. A range error may occur.
11160 The hypot functions return (sqrt)x2 + y2 .
11161 <pre>
11162 ???
11163 ???????????????</pre>
11168 <pre>
11170 double pow(double x, double y);
11171 float powf(float x, float y);
11172 long double powl(long double x, long double y);</pre>
11175 The pow functions compute x raised to the power y. A domain error occurs if x is finite
11176 and negative and y is finite and not an integer value. A range error may occur. A domain
11177 error may occur if x is zero and y is zero. A domain error or range error may occur if x
11178 is zero and y is less than zero.
11181 The pow functions return xy .
11186 <!--page 242 -->
11187 <pre>
11189 double sqrt(double x);
11190 float sqrtf(float x);
11191 long double sqrtl(long double x);</pre>
11194 The sqrt functions compute the nonnegative square root of x. A domain error occurs if
11195 the argument is less than zero.
11198 The sqrt functions return (sqrt)x.
11199 <pre>
11200 ???
11201 ???</pre>
11208 <pre>
11210 double erf(double x);
11211 float erff(float x);
11212 long double erfl(long double x);</pre>
11215 The erf functions compute the error function of x.
11217 <pre>
11218 2 x
11219 (integral)</pre>
11221 The erf functions return erf x = e-t dt.
11222 <pre>
11226 <pre>
11227 (sqrt)pi
11228 ???
11235 <pre>
11237 double erfc(double x);
11238 float erfcf(float x);
11239 long double erfcl(long double x);</pre>
11242 The erfc functions compute the complementary error function of x. A range error
11243 occurs if x is too large.
11245 <pre>
11246 2 (inf)
11247 (integral)</pre>
11249 The erfc functions return erfc x = 1 - erf x = e-t dt.
11250 <pre>
11254 <!--page 243 -->
11255 <pre>
11256 (sqrt)pi
11257 ???
11258 ??? x</pre>
11263 <pre>
11265 double lgamma(double x);
11266 float lgammaf(float x);
11267 long double lgammal(long double x);</pre>
11270 The lgamma functions compute the natural logarithm of the absolute value of gamma of
11271 x. A range error occurs if x is too large. A range error may occur if x is a negative
11272 integer or zero.
11275 The lgamma functions return loge | (Gamma)(x) |.
11280 <pre>
11282 double tgamma(double x);
11283 float tgammaf(float x);
11284 long double tgammal(long double x);</pre>
11287 The tgamma functions compute the gamma function of x. A domain error or range error
11288 may occur if x is a negative integer or zero. A range error may occur if the magnitude of
11289 x is too large or too small.
11292 The tgamma functions return (Gamma)(x).
11299 <pre>
11301 double ceil(double x);
11302 float ceilf(float x);
11303 long double ceill(long double x);</pre>
11306 The ceil functions compute the smallest integer value not less than x.
11307 <!--page 244 -->
11310 The ceil functions return ???x???, expressed as a floating-point number.
11315 <pre>
11317 double floor(double x);
11318 float floorf(float x);
11319 long double floorl(long double x);</pre>
11322 The floor functions compute the largest integer value not greater than x.
11325 The floor functions return ???x???, expressed as a floating-point number.
11330 <pre>
11332 double nearbyint(double x);
11333 float nearbyintf(float x);
11334 long double nearbyintl(long double x);</pre>
11337 The nearbyint functions round their argument to an integer value in floating-point
11338 format, using the current rounding direction and without raising the ''inexact'' floating-
11339 point exception.
11342 The nearbyint functions return the rounded integer value.
11347 <pre>
11349 double rint(double x);
11350 float rintf(float x);
11351 long double rintl(long double x);</pre>
11354 The rint functions differ from the nearbyint functions (<a href="#7.12.9.3">7.12.9.3</a>) only in that the
11355 rint functions may raise the ''inexact'' floating-point exception if the result differs in
11356 value from the argument.
11357 <!--page 245 -->
11360 The rint functions return the rounded integer value.
11365 <pre>
11367 long int lrint(double x);
11368 long int lrintf(float x);
11369 long int lrintl(long double x);
11370 long long int llrint(double x);
11371 long long int llrintf(float x);
11372 long long int llrintl(long double x);</pre>
11375 The lrint and llrint functions round their argument to the nearest integer value,
11376 rounding according to the current rounding direction. If the rounded value is outside the
11377 range of the return type, the numeric result is unspecified and a domain error or range
11378 error may occur. *
11381 The lrint and llrint functions return the rounded integer value.
11386 <pre>
11388 double round(double x);
11389 float roundf(float x);
11390 long double roundl(long double x);</pre>
11393 The round functions round their argument to the nearest integer value in floating-point
11394 format, rounding halfway cases away from zero, regardless of the current rounding
11395 direction.
11398 The round functions return the rounded integer value.
11399 <!--page 246 -->
11404 <pre>
11406 long int lround(double x);
11407 long int lroundf(float x);
11408 long int lroundl(long double x);
11409 long long int llround(double x);
11410 long long int llroundf(float x);
11411 long long int llroundl(long double x);</pre>
11414 The lround and llround functions round their argument to the nearest integer value,
11415 rounding halfway cases away from zero, regardless of the current rounding direction. If
11416 the rounded value is outside the range of the return type, the numeric result is unspecified
11417 and a domain error or range error may occur.
11420 The lround and llround functions return the rounded integer value.
11425 <pre>
11427 double trunc(double x);
11428 float truncf(float x);
11429 long double truncl(long double x);</pre>
11432 The trunc functions round their argument to the integer value, in floating format,
11433 nearest to but no larger in magnitude than the argument.
11436 The trunc functions return the truncated integer value.
11437 <!--page 247 -->
11444 <pre>
11446 double fmod(double x, double y);
11447 float fmodf(float x, float y);
11448 long double fmodl(long double x, long double y);</pre>
11451 The fmod functions compute the floating-point remainder of x/y.
11454 The fmod functions return the value x - ny, for some integer n such that, if y is nonzero,
11455 the result has the same sign as x and magnitude less than the magnitude of y. If y is zero,
11456 whether a domain error occurs or the fmod functions return zero is implementation-
11457 defined.
11462 <pre>
11464 double remainder(double x, double y);
11465 float remainderf(float x, float y);
11466 long double remainderl(long double x, long double y);</pre>
11469 The remainder functions compute the remainder x REM y required by IEC 60559.<sup><a href="#note210"><b>210)</b></a></sup>
11472 The remainder functions return x REM y. If y is zero, whether a domain error occurs
11473 or the functions return zero is implementation defined.
11478 <!--page 248 -->
11481 <p><small><a name="note210" href="#note210">210)</a> ''When y != 0, the remainder r = x REM y is defined regardless of the rounding mode by the
11482 mathematical relation r = x - ny, where n is the integer nearest the exact value of x/y; whenever
11483 | n - x/y | = 1/2, then n is even. Thus, the remainder is always exact. If r = 0, its sign shall be that of
11484 x.'' This definition is applicable for all implementations.
11485 </small>
11490 <pre>
11492 double remquo(double x, double y, int *quo);
11493 float remquof(float x, float y, int *quo);
11494 long double remquol(long double x, long double y,
11495 int *quo);</pre>
11498 The remquo functions compute the same remainder as the remainder functions. In
11499 the object pointed to by quo they store a value whose sign is the sign of x/y and whose
11500 magnitude is congruent modulo 2n to the magnitude of the integral quotient of x/y, where
11501 n is an implementation-defined integer greater than or equal to 3.
11504 The remquo functions return x REM y. If y is zero, the value stored in the object
11505 pointed to by quo is unspecified and whether a domain error occurs or the functions
11506 return zero is implementation defined.
11513 <pre>
11515 double copysign(double x, double y);
11516 float copysignf(float x, float y);
11517 long double copysignl(long double x, long double y);</pre>
11520 The copysign functions produce a value with the magnitude of x and the sign of y.
11521 They produce a NaN (with the sign of y) if x is a NaN. On implementations that
11522 represent a signed zero but do not treat negative zero consistently in arithmetic
11523 operations, the copysign functions regard the sign of zero as positive.
11526 The copysign functions return a value with the magnitude of x and the sign of y.
11527 <!--page 249 -->
11532 <pre>
11534 double nan(const char *tagp);
11535 float nanf(const char *tagp);
11536 long double nanl(const char *tagp);</pre>
11541 strtod("NAN()", (char**) NULL). If tagp does not point to an n-char
11542 sequence or an empty string, the call is equivalent to strtod("NAN", (char**)
11543 NULL). Calls to nanf and nanl are equivalent to the corresponding calls to strtof
11544 and strtold.
11547 The nan functions return a quiet NaN, if available, with content indicated through tagp.
11548 If the implementation does not support quiet NaNs, the functions return zero.
11549 <p><b> Forward references</b>: the strtod, strtof, and strtold functions (<a href="#7.20.1.3">7.20.1.3</a>).
11554 <pre>
11556 double nextafter(double x, double y);
11557 float nextafterf(float x, float y);
11558 long double nextafterl(long double x, long double y);</pre>
11561 The nextafter functions determine the next representable value, in the type of the
11562 function, after x in the direction of y, where x and y are first converted to the type of the
11563 function.<sup><a href="#note211"><b>211)</b></a></sup> The nextafter functions return y if x equals y. A range error may occur
11564 if the magnitude of x is the largest finite value representable in the type and the result is
11565 infinite or not representable in the type.
11568 The nextafter functions return the next representable value in the specified format
11569 after x in the direction of y.
11572 <!--page 250 -->
11575 <p><small><a name="note211" href="#note211">211)</a> The argument values are converted to the type of the function, even by a macro implementation of the
11576 function.
11577 </small>
11582 <pre>
11584 double nexttoward(double x, long double y);
11585 float nexttowardf(float x, long double y);
11586 long double nexttowardl(long double x, long double y);</pre>
11589 The nexttoward functions are equivalent to the nextafter functions except that the
11590 second parameter has type long double and the functions return y converted to the
11594 <p><small><a name="note212" href="#note212">212)</a> The result of the nexttoward functions is determined in the type of the function, without loss of
11595 range or precision in a floating second argument.
11596 </small>
11598 <h4><a name="7.12.12" href="#7.12.12">7.12.12 Maximum, minimum, and positive difference functions</a></h4>
11603 <pre>
11605 double fdim(double x, double y);
11606 float fdimf(float x, float y);
11607 long double fdiml(long double x, long double y);</pre>
11610 The fdim functions determine the positive difference between their arguments:
11611 <pre>
11612 ???x - y if x > y
11613 ???
11615 A range error may occur.
11618 The fdim functions return the positive difference value.
11623 <pre>
11625 double fmax(double x, double y);
11626 float fmaxf(float x, float y);
11627 long double fmaxl(long double x, long double y);</pre>
11631 <!--page 251 -->
11634 The fmax functions determine the maximum numeric value of their arguments.<sup><a href="#note213"><b>213)</b></a></sup>
11637 The fmax functions return the maximum numeric value of their arguments.
11640 <p><small><a name="note213" href="#note213">213)</a> NaN arguments are treated as missing data: if one argument is a NaN and the other numeric, then the
11642 </small>
11647 <pre>
11649 double fmin(double x, double y);
11650 float fminf(float x, float y);
11651 long double fminl(long double x, long double y);</pre>
11654 The fmin functions determine the minimum numeric value of their arguments.<sup><a href="#note214"><b>214)</b></a></sup>
11657 The fmin functions return the minimum numeric value of their arguments.
11660 <p><small><a name="note214" href="#note214">214)</a> The fmin functions are analogous to the fmax functions in their treatment of NaNs.
11661 </small>
11668 <pre>
11670 double fma(double x, double y, double z);
11671 float fmaf(float x, float y, float z);
11672 long double fmal(long double x, long double y,
11673 long double z);</pre>
11676 The fma functions compute (x x y) + z, rounded as one ternary operation: they compute
11677 the value (as if) to infinite precision and round once to the result format, according to the
11678 current rounding mode. A range error may occur.
11681 The fma functions return (x x y) + z, rounded as one ternary operation.
11686 <!--page 252 -->
11690 The relational and equality operators support the usual mathematical relationships
11691 between numeric values. For any ordered pair of numeric values exactly one of the
11692 relationships -- less, greater, and equal -- is true. Relational operators may raise the
11693 ''invalid'' floating-point exception when argument values are NaNs. For a NaN and a
11694 numeric value, or for two NaNs, just the unordered relationship is true.<sup><a href="#note215"><b>215)</b></a></sup> The following
11695 subclauses provide macros that are quiet (non floating-point exception raising) versions
11696 of the relational operators, and other comparison macros that facilitate writing efficient
11697 code that accounts for NaNs without suffering the ''invalid'' floating-point exception. In
11698 the synopses in this subclause, real-floating indicates that the argument shall be an
11699 expression of real floating type.
11702 <p><small><a name="note215" href="#note215">215)</a> IEC 60559 requires that the built-in relational operators raise the ''invalid'' floating-point exception if
11703 the operands compare unordered, as an error indicator for programs written without consideration of
11704 NaNs; the result in these cases is false.
11705 </small>
11710 <pre>
11712 int isgreater(real-floating x, real-floating y);</pre>
11715 The isgreater macro determines whether its first argument is greater than its second
11716 argument. The value of isgreater(x, y) is always equal to (x) > (y); however,
11717 unlike (x) > (y), isgreater(x, y) does not raise the ''invalid'' floating-point
11718 exception when x and y are unordered.
11721 The isgreater macro returns the value of (x) > (y).
11726 <pre>
11728 int isgreaterequal(real-floating x, real-floating y);</pre>
11731 The isgreaterequal macro determines whether its first argument is greater than or
11732 equal to its second argument. The value of isgreaterequal(x, y) is always equal
11734 not raise the ''invalid'' floating-point exception when x and y are unordered.
11738 <!--page 253 -->
11741 The isgreaterequal macro returns the value of (x) >= (y).
11746 <pre>
11748 int isless(real-floating x, real-floating y);</pre>
11751 The isless macro determines whether its first argument is less than its second
11752 argument. The value of isless(x, y) is always equal to (x) < (y); however,
11753 unlike (x) < (y), isless(x, y) does not raise the ''invalid'' floating-point
11754 exception when x and y are unordered.
11757 The isless macro returns the value of (x) < (y).
11762 <pre>
11764 int islessequal(real-floating x, real-floating y);</pre>
11767 The islessequal macro determines whether its first argument is less than or equal to
11768 its second argument. The value of islessequal(x, y) is always equal to
11770 the ''invalid'' floating-point exception when x and y are unordered.
11773 The islessequal macro returns the value of (x) <= (y).
11778 <pre>
11780 int islessgreater(real-floating x, real-floating y);</pre>
11783 The islessgreater macro determines whether its first argument is less than or
11784 greater than its second argument. The islessgreater(x, y) macro is similar to
11786 the ''invalid'' floating-point exception when x and y are unordered (nor does it evaluate x
11787 and y twice).
11788 <!--page 254 -->
11796 <pre>
11798 int isunordered(real-floating x, real-floating y);</pre>
11801 The isunordered macro determines whether its arguments are unordered.
11805 <!--page 255 -->
11809 The header <a href="#7.13"><setjmp.h></a> defines the macro setjmp, and declares one function and
11810 one type, for bypassing the normal function call and return discipline.<sup><a href="#note216"><b>216)</b></a></sup>
11812 The type declared is
11813 <pre>
11814 jmp_buf</pre>
11815 which is an array type suitable for holding the information needed to restore a calling
11816 environment. The environment of a call to the setjmp macro consists of information
11817 sufficient for a call to the longjmp function to return execution to the correct block and
11818 invocation of that block, were it called recursively. It does not include the state of the
11819 floating-point status flags, of open files, or of any other component of the abstract
11820 machine.
11822 It is unspecified whether setjmp is a macro or an identifier declared with external
11823 linkage. If a macro definition is suppressed in order to access an actual function, or a
11824 program defines an external identifier with the name setjmp, the behavior is undefined.
11827 <p><small><a name="note216" href="#note216">216)</a> These functions are useful for dealing with unusual conditions encountered in a low-level function of
11828 a program.
11829 </small>
11836 <pre>
11838 int setjmp(jmp_buf env);</pre>
11841 The setjmp macro saves its calling environment in its jmp_buf argument for later use
11842 by the longjmp function.
11845 If the return is from a direct invocation, the setjmp macro returns the value zero. If the
11846 return is from a call to the longjmp function, the setjmp macro returns a nonzero
11847 value.
11848 Environmental limits
11850 An invocation of the setjmp macro shall appear only in one of the following contexts:
11851 <ul>
11852 <li> the entire controlling expression of a selection or iteration statement;
11853 <li> one operand of a relational or equality operator with the other operand an integer
11854 constant expression, with the resulting expression being the entire controlling
11857 <!--page 256 -->
11858 expression of a selection or iteration statement;
11859 <li> the operand of a unary ! operator with the resulting expression being the entire
11860 controlling expression of a selection or iteration statement; or
11861 <li> the entire expression of an expression statement (possibly cast to void).
11862 </ul>
11864 If the invocation appears in any other context, the behavior is undefined.
11871 <pre>
11873 void longjmp(jmp_buf env, int val);</pre>
11876 The longjmp function restores the environment saved by the most recent invocation of
11877 the setjmp macro in the same invocation of the program with the corresponding
11878 jmp_buf argument. If there has been no such invocation, or if the function containing
11879 the invocation of the setjmp macro has terminated execution<sup><a href="#note217"><b>217)</b></a></sup> in the interim, or if the
11880 invocation of the setjmp macro was within the scope of an identifier with variably
11881 modified type and execution has left that scope in the interim, the behavior is undefined.
11883 All accessible objects have values, and all other components of the abstract machine<sup><a href="#note218"><b>218)</b></a></sup>
11884 have state, as of the time the longjmp function was called, except that the values of
11885 objects of automatic storage duration that are local to the function containing the
11886 invocation of the corresponding setjmp macro that do not have volatile-qualified type
11887 and have been changed between the setjmp invocation and longjmp call are
11888 indeterminate.
11891 After longjmp is completed, program execution continues as if the corresponding
11892 invocation of the setjmp macro had just returned the value specified by val. The
11894 the setjmp macro returns the value 1.
11896 EXAMPLE The longjmp function that returns control back to the point of the setjmp invocation
11897 might cause memory associated with a variable length array object to be squandered.
11902 <!--page 257 -->
11903 <!--page 258 -->
11904 <pre>
11906 jmp_buf buf;
11907 void g(int n);
11908 void h(int n);
11909 int n = 6;
11910 void f(void)
11911 {
11912 int x[n]; // valid: f is not terminated
11913 setjmp(buf);
11914 g(n);
11915 }
11916 void g(int n)
11917 {
11918 int a[n]; // a may remain allocated
11919 h(n);
11920 }
11921 void h(int n)
11922 {
11923 int b[n]; // b may remain allocated
11924 longjmp(buf, 2); // might cause memory loss
11925 }</pre>
11928 <p><small><a name="note217" href="#note217">217)</a> For example, by executing a return statement or because another longjmp call has caused a
11929 transfer to a setjmp invocation in a function earlier in the set of nested calls.
11930 </small>
11931 <p><small><a name="note218" href="#note218">218)</a> This includes, but is not limited to, the floating-point status flags and the state of open files.
11932 </small>
11936 The header <a href="#7.14"><signal.h></a> declares a type and two functions and defines several macros,
11937 for handling various signals (conditions that may be reported during program execution).
11939 The type defined is
11940 <pre>
11941 sig_atomic_t</pre>
11942 which is the (possibly volatile-qualified) integer type of an object that can be accessed as
11943 an atomic entity, even in the presence of asynchronous interrupts.
11945 The macros defined are
11946 <pre>
11947 SIG_DFL
11948 SIG_ERR
11949 SIG_IGN</pre>
11950 which expand to constant expressions with distinct values that have type compatible with
11951 the second argument to, and the return value of, the signal function, and whose values
11952 compare unequal to the address of any declarable function; and the following, which
11953 expand to positive integer constant expressions with type int and distinct values that are
11954 the signal numbers, each corresponding to the specified condition:
11956 <pre>
11957 SIGABRT abnormal termination, such as is initiated by the abort function
11958 SIGFPE an erroneous arithmetic operation, such as zero divide or an operation
11959 resulting in overflow
11960 SIGILL detection of an invalid function image, such as an invalid instruction
11961 SIGINT receipt of an interactive attention signal
11962 SIGSEGV an invalid access to storage
11963 SIGTERM a termination request sent to the program</pre>
11964 An implementation need not generate any of these signals, except as a result of explicit
11965 calls to the raise function. Additional signals and pointers to undeclarable functions,
11966 with macro definitions beginning, respectively, with the letters SIG and an uppercase
11967 letter or with SIG_ and an uppercase letter,<sup><a href="#note219"><b>219)</b></a></sup> may also be specified by the
11968 implementation. The complete set of signals, their semantics, and their default handling
11969 is implementation-defined; all signal numbers shall be positive.
11974 <!--page 259 -->
11977 <p><small><a name="note219" href="#note219">219)</a> See ''future library directions'' (<a href="#7.26.9">7.26.9</a>). The names of the signal numbers reflect the following terms
11978 (respectively): abort, floating-point exception, illegal instruction, interrupt, segmentation violation,
11979 and termination.
11980 </small>
11987 <pre>
11989 void (*signal(int sig, void (*func)(int)))(int);</pre>
11992 The signal function chooses one of three ways in which receipt of the signal number
11993 sig is to be subsequently handled. If the value of func is SIG_DFL, default handling
11994 for that signal will occur. If the value of func is SIG_IGN, the signal will be ignored.
11995 Otherwise, func shall point to a function to be called when that signal occurs. An
11996 invocation of such a function because of a signal, or (recursively) of any further functions
11997 called by that invocation (other than functions in the standard library), is called a signal
11998 handler.
12000 When a signal occurs and func points to a function, it is implementation-defined
12001 whether the equivalent of signal(sig, SIG_DFL); is executed or the
12002 implementation prevents some implementation-defined set of signals (at least including
12003 sig) from occurring until the current signal handling has completed; in the case of
12004 SIGILL, the implementation may alternatively define that no action is taken. Then the
12005 equivalent of (*func)(sig); is executed. If and when the function returns, if the
12006 value of sig is SIGFPE, SIGILL, SIGSEGV, or any other implementation-defined
12007 value corresponding to a computational exception, the behavior is undefined; otherwise
12008 the program will resume execution at the point it was interrupted.
12010 If the signal occurs as the result of calling the abort or raise function, the signal
12011 handler shall not call the raise function.
12013 If the signal occurs other than as the result of calling the abort or raise function, the
12014 behavior is undefined if the signal handler refers to any object with static storage duration
12015 other than by assigning a value to an object declared as volatile sig_atomic_t, or
12016 the signal handler calls any function in the standard library other than the abort
12017 function, the _Exit function, or the signal function with the first argument equal to
12018 the signal number corresponding to the signal that caused the invocation of the handler.
12019 Furthermore, if such a call to the signal function results in a SIG_ERR return, the
12022 At program startup, the equivalent of
12023 <pre>
12024 signal(sig, SIG_IGN);</pre>
12027 <!--page 260 -->
12028 may be executed for some signals selected in an implementation-defined manner; the
12029 equivalent of
12030 <pre>
12031 signal(sig, SIG_DFL);</pre>
12032 is executed for all other signals defined by the implementation.
12034 The implementation shall behave as if no library function calls the signal function.
12037 If the request can be honored, the signal function returns the value of func for the
12038 most recent successful call to signal for the specified signal sig. Otherwise, a value of
12039 SIG_ERR is returned and a positive value is stored in errno.
12040 <p><b> Forward references</b>: the abort function (<a href="#7.20.4.1">7.20.4.1</a>), the exit function (<a href="#7.20.4.3">7.20.4.3</a>), the
12044 <p><small><a name="note220" href="#note220">220)</a> If any signal is generated by an asynchronous signal handler, the behavior is undefined.
12045 </small>
12052 <pre>
12054 int raise(int sig);</pre>
12057 The raise function carries out the actions described in <a href="#7.14.1.1">7.14.1.1</a> for the signal sig. If a
12058 signal handler is called, the raise function shall not return until after the signal handler
12059 does.
12062 The raise function returns zero if successful, nonzero if unsuccessful.
12063 <!--page 261 -->
12067 The header <a href="#7.15"><stdarg.h></a> declares a type and defines four macros, for advancing
12068 through a list of arguments whose number and types are not known to the called function
12069 when it is translated.
12071 A function may be called with a variable number of arguments of varying types. As
12072 described in <a href="#6.9.1">6.9.1</a>, its parameter list contains one or more parameters. The rightmost
12073 parameter plays a special role in the access mechanism, and will be designated parmN in
12074 this description.
12076 The type declared is
12077 <pre>
12078 va_list</pre>
12079 which is an object type suitable for holding information needed by the macros
12080 va_start, va_arg, va_end, and va_copy. If access to the varying arguments is
12081 desired, the called function shall declare an object (generally referred to as ap in this
12082 subclause) having type va_list. The object ap may be passed as an argument to
12083 another function; if that function invokes the va_arg macro with parameter ap, the
12084 value of ap in the calling function is indeterminate and shall be passed to the va_end
12088 <p><small><a name="note221" href="#note221">221)</a> It is permitted to create a pointer to a va_list and pass that pointer to another function, in which
12089 case the original function may make further use of the original list after the other function returns.
12090 </small>
12094 The va_start and va_arg macros described in this subclause shall be implemented
12095 as macros, not functions. It is unspecified whether va_copy and va_end are macros or
12096 identifiers declared with external linkage. If a macro definition is suppressed in order to
12097 access an actual function, or a program defines an external identifier with the same name,
12098 the behavior is undefined. Each invocation of the va_start and va_copy macros
12099 shall be matched by a corresponding invocation of the va_end macro in the same
12100 function.
12105 <pre>
12107 type va_arg(va_list ap, type);</pre>
12110 The va_arg macro expands to an expression that has the specified type and the value of
12111 the next argument in the call. The parameter ap shall have been initialized by the
12112 va_start or va_copy macro (without an intervening invocation of the va_end
12114 <!--page 262 -->
12115 macro for the same ap). Each invocation of the va_arg macro modifies ap so that the
12116 values of successive arguments are returned in turn. The parameter type shall be a type
12117 name specified such that the type of a pointer to an object that has the specified type can
12118 be obtained simply by postfixing a * to type. If there is no actual next argument, or if
12119 type is not compatible with the type of the actual next argument (as promoted according
12120 to the default argument promotions), the behavior is undefined, except for the following
12121 cases:
12122 <ul>
12123 <li> one type is a signed integer type, the other type is the corresponding unsigned integer
12124 type, and the value is representable in both types;
12125 <li> one type is pointer to void and the other is a pointer to a character type.
12126 </ul>
12129 The first invocation of the va_arg macro after that of the va_start macro returns the
12130 value of the argument after that specified by parmN . Successive invocations return the
12131 values of the remaining arguments in succession.
12136 <pre>
12138 void va_copy(va_list dest, va_list src);</pre>
12141 The va_copy macro initializes dest as a copy of src, as if the va_start macro had
12142 been applied to dest followed by the same sequence of uses of the va_arg macro as
12143 had previously been used to reach the present state of src. Neither the va_copy nor
12144 va_start macro shall be invoked to reinitialize dest without an intervening
12145 invocation of the va_end macro for the same dest.
12148 The va_copy macro returns no value.
12153 <pre>
12155 void va_end(va_list ap);</pre>
12158 The va_end macro facilitates a normal return from the function whose variable
12159 argument list was referred to by the expansion of the va_start macro, or the function
12160 containing the expansion of the va_copy macro, that initialized the va_list ap. The
12161 va_end macro may modify ap so that it is no longer usable (without being reinitialized
12162 <!--page 263 -->
12163 by the va_start or va_copy macro). If there is no corresponding invocation of the
12164 va_start or va_copy macro, or if the va_end macro is not invoked before the
12165 return, the behavior is undefined.
12168 The va_end macro returns no value.
12173 <pre>
12175 void va_start(va_list ap, parmN);</pre>
12178 The va_start macro shall be invoked before any access to the unnamed arguments.
12180 The va_start macro initializes ap for subsequent use by the va_arg and va_end
12181 macros. Neither the va_start nor va_copy macro shall be invoked to reinitialize ap
12182 without an intervening invocation of the va_end macro for the same ap.
12184 The parameter parmN is the identifier of the rightmost parameter in the variable
12185 parameter list in the function definition (the one just before the , ...). If the parameter
12186 parmN is declared with the register storage class, with a function or array type, or
12187 with a type that is not compatible with the type that results after application of the default
12188 argument promotions, the behavior is undefined.
12191 The va_start macro returns no value.
12193 EXAMPLE 1 The function f1 gathers into an array a list of arguments that are pointers to strings (but not
12194 more than MAXARGS arguments), then passes the array as a single argument to function f2. The number of
12195 pointers is specified by the first argument to f1.
12196 <!--page 264 -->
12197 <pre>
12199 #define MAXARGS 31
12200 void f1(int n_ptrs, ...)
12201 {
12202 va_list ap;
12203 char *array[MAXARGS];
12204 int ptr_no = 0;
12205 if (n_ptrs > MAXARGS)
12206 n_ptrs = MAXARGS;
12207 va_start(ap, n_ptrs);
12208 while (ptr_no < n_ptrs)
12209 array[ptr_no++] = va_arg(ap, char *);
12210 va_end(ap);
12211 f2(n_ptrs, array);
12212 }</pre>
12213 Each call to f1 is required to have visible the definition of the function or a declaration such as
12214 <pre>
12215 void f1(int, ...);</pre>
12218 EXAMPLE 2 The function f3 is similar, but saves the status of the variable argument list after the
12219 indicated number of arguments; after f2 has been called once with the whole list, the trailing part of the list
12220 is gathered again and passed to function f4.
12221 <!--page 265 -->
12222 <pre>
12224 #define MAXARGS 31
12225 void f3(int n_ptrs, int f4_after, ...)
12226 {
12227 va_list ap, ap_save;
12228 char *array[MAXARGS];
12229 int ptr_no = 0;
12230 if (n_ptrs > MAXARGS)
12231 n_ptrs = MAXARGS;
12232 va_start(ap, f4_after);
12233 while (ptr_no < n_ptrs) {
12234 array[ptr_no++] = va_arg(ap, char *);
12235 if (ptr_no == f4_after)
12236 va_copy(ap_save, ap);
12237 }
12238 va_end(ap);
12239 f2(n_ptrs, array);
12240 // Now process the saved copy.
12241 n_ptrs -= f4_after;
12242 ptr_no = 0;
12243 while (ptr_no < n_ptrs)
12244 array[ptr_no++] = va_arg(ap_save, char *);
12245 va_end(ap_save);
12246 f4(n_ptrs, array);
12247 }</pre>
12253 The macro
12254 <pre>
12255 bool</pre>
12256 expands to _Bool.
12258 The remaining three macros are suitable for use in #if preprocessing directives. They
12259 are
12260 <pre>
12261 true</pre>
12262 which expands to the integer constant 1,
12263 <pre>
12264 false</pre>
12265 which expands to the integer constant 0, and
12266 <pre>
12267 __bool_true_false_are_defined</pre>
12268 which expands to the integer constant 1.
12270 Notwithstanding the provisions of <a href="#7.1.3">7.1.3</a>, a program may undefine and perhaps then
12276 <!--page 266 -->
12279 <p><small><a name="note222" href="#note222">222)</a> See ''future library directions'' (<a href="#7.26.7">7.26.7</a>).
12280 </small>
12284 The following types and macros are defined in the standard header <a href="#7.17"><stddef.h></a>. Some
12285 are also defined in other headers, as noted in their respective subclauses.
12287 The types are
12288 <pre>
12289 ptrdiff_t</pre>
12290 which is the signed integer type of the result of subtracting two pointers;
12291 <pre>
12292 size_t</pre>
12293 which is the unsigned integer type of the result of the sizeof operator; and
12294 <pre>
12295 wchar_t</pre>
12296 which is an integer type whose range of values can represent distinct codes for all
12297 members of the largest extended character set specified among the supported locales; the
12298 null character shall have the code value zero. Each member of the basic character set
12299 shall have a code value equal to its value when used as the lone character in an integer
12300 character constant if an implementation does not define
12301 __STDC_MB_MIGHT_NEQ_WC__.
12303 The macros are
12304 <pre>
12305 NULL</pre>
12306 which expands to an implementation-defined null pointer constant; and
12307 <pre>
12308 offsetof(type, member-designator)</pre>
12309 which expands to an integer constant expression that has type size_t, the value of
12310 which is the offset in bytes, to the structure member (designated by member-designator),
12311 from the beginning of its structure (designated by type). The type and member designator
12312 shall be such that given
12313 <pre>
12314 static type t;</pre>
12315 then the expression &(t.member-designator) evaluates to an address constant. (If the
12316 specified member is a bit-field, the behavior is undefined.)
12317 Recommended practice
12319 The types used for size_t and ptrdiff_t should not have an integer conversion rank
12320 greater than that of signed long int unless the implementation supports objects
12321 large enough to make this necessary.
12323 <!--page 267 -->
12327 The header <a href="#7.18"><stdint.h></a> declares sets of integer types having specified widths, and
12328 defines corresponding sets of macros.<sup><a href="#note223"><b>223)</b></a></sup> It also defines macros that specify limits of
12329 integer types corresponding to types defined in other standard headers.
12331 Types are defined in the following categories:
12332 <ul>
12333 <li> integer types having certain exact widths;
12334 <li> integer types having at least certain specified widths;
12335 <li> fastest integer types having at least certain specified widths;
12336 <li> integer types wide enough to hold pointers to objects;
12337 <li> integer types having greatest width.
12338 </ul>
12339 (Some of these types may denote the same type.)
12341 Corresponding macros specify limits of the declared types and construct suitable
12342 constants.
12344 For each type described herein that the implementation provides,<sup><a href="#note224"><b>224)</b></a></sup> <a href="#7.18"><stdint.h></a> shall
12345 declare that typedef name and define the associated macros. Conversely, for each type
12346 described herein that the implementation does not provide, <a href="#7.18"><stdint.h></a> shall not
12347 declare that typedef name nor shall it define the associated macros. An implementation
12348 shall provide those types described as ''required'', but need not provide any of the others
12349 (described as ''optional'').
12352 <p><small><a name="note223" href="#note223">223)</a> See ''future library directions'' (<a href="#7.26.8">7.26.8</a>).
12353 </small>
12354 <p><small><a name="note224" href="#note224">224)</a> Some of these types may denote implementation-defined extended integer types.
12355 </small>
12359 When typedef names differing only in the absence or presence of the initial u are defined,
12360 they shall denote corresponding signed and unsigned types as described in <a href="#6.2.5">6.2.5</a>; an
12361 implementation providing one of these corresponding types shall also provide the other.
12363 In the following descriptions, the symbol N represents an unsigned decimal integer with
12369 <!--page 268 -->
12373 The typedef name intN_t designates a signed integer type with width N , no padding
12374 bits, and a two's complement representation. Thus, int8_t denotes a signed integer
12375 type with a width of exactly 8 bits.
12377 The typedef name uintN_t designates an unsigned integer type with width N . Thus,
12378 uint24_t denotes an unsigned integer type with a width of exactly 24 bits.
12380 These types are optional. However, if an implementation provides integer types with
12382 two's complement representation, it shall define the corresponding typedef names.
12386 The typedef name int_leastN_t designates a signed integer type with a width of at
12387 least N , such that no signed integer type with lesser size has at least the specified width.
12388 Thus, int_least32_t denotes a signed integer type with a width of at least 32 bits.
12390 The typedef name uint_leastN_t designates an unsigned integer type with a width
12391 of at least N , such that no unsigned integer type with lesser size has at least the specified
12392 width. Thus, uint_least16_t denotes an unsigned integer type with a width of at
12393 least 16 bits.
12395 The following types are required:
12396 <pre>
12397 int_least8_t uint_least8_t
12398 int_least16_t uint_least16_t
12399 int_least32_t uint_least32_t
12400 int_least64_t uint_least64_t</pre>
12401 All other types of this form are optional.
12405 Each of the following types designates an integer type that is usually fastest<sup><a href="#note225"><b>225)</b></a></sup> to operate
12406 with among all integer types that have at least the specified width.
12408 The typedef name int_fastN_t designates the fastest signed integer type with a width
12409 of at least N . The typedef name uint_fastN_t designates the fastest unsigned integer
12410 type with a width of at least N .
12415 <!--page 269 -->
12417 The following types are required:
12418 <pre>
12419 int_fast8_t uint_fast8_t
12420 int_fast16_t uint_fast16_t
12421 int_fast32_t uint_fast32_t
12422 int_fast64_t uint_fast64_t</pre>
12423 All other types of this form are optional.
12426 <p><small><a name="note225" href="#note225">225)</a> The designated type is not guaranteed to be fastest for all purposes; if the implementation has no clear
12427 grounds for choosing one type over another, it will simply pick some integer type satisfying the
12428 signedness and width requirements.
12429 </small>
12431 <h5><a name="7.18.1.4" href="#7.18.1.4">7.18.1.4 Integer types capable of holding object pointers</a></h5>
12433 The following type designates a signed integer type with the property that any valid
12434 pointer to void can be converted to this type, then converted back to pointer to void,
12435 and the result will compare equal to the original pointer:
12436 <pre>
12437 intptr_t</pre>
12438 The following type designates an unsigned integer type with the property that any valid
12439 pointer to void can be converted to this type, then converted back to pointer to void,
12440 and the result will compare equal to the original pointer:
12441 <pre>
12442 uintptr_t</pre>
12443 These types are optional.
12447 The following type designates a signed integer type capable of representing any value of
12448 any signed integer type:
12449 <pre>
12450 intmax_t</pre>
12451 The following type designates an unsigned integer type capable of representing any value
12452 of any unsigned integer type:
12453 <pre>
12454 uintmax_t</pre>
12455 These types are required.
12459 The following object-like macros<sup><a href="#note226"><b>226)</b></a></sup> specify the minimum and maximum limits of the
12460 types declared in <a href="#7.18"><stdint.h></a>. Each macro name corresponds to a similar type name in
12463 Each instance of any defined macro shall be replaced by a constant expression suitable
12464 for use in #if preprocessing directives, and this expression shall have the same type as
12465 would an expression that is an object of the corresponding type converted according to
12467 <!--page 270 -->
12468 the integer promotions. Its implementation-defined value shall be equal to or greater in
12469 magnitude (absolute value) than the corresponding value given below, with the same sign,
12470 except where stated to be exactly the given value.
12473 <p><small><a name="note226" href="#note226">226)</a> C++ implementations should define these macros only when __STDC_LIMIT_MACROS is defined
12475 </small>
12479 <ul>
12480 <li> minimum values of exact-width signed integer types
12482 <li> maximum values of exact-width signed integer types
12484 <li> maximum values of exact-width unsigned integer types
12486 </ul>
12488 <h5><a name="7.18.2.2" href="#7.18.2.2">7.18.2.2 Limits of minimum-width integer types</a></h5>
12490 <ul>
12491 <li> minimum values of minimum-width signed integer types
12493 <li> maximum values of minimum-width signed integer types
12495 <li> maximum values of minimum-width unsigned integer types
12497 </ul>
12499 <h5><a name="7.18.2.3" href="#7.18.2.3">7.18.2.3 Limits of fastest minimum-width integer types</a></h5>
12501 <ul>
12502 <li> minimum values of fastest minimum-width signed integer types
12504 <li> maximum values of fastest minimum-width signed integer types
12506 <li> maximum values of fastest minimum-width unsigned integer types
12508 </ul>
12510 <h5><a name="7.18.2.4" href="#7.18.2.4">7.18.2.4 Limits of integer types capable of holding object pointers</a></h5>
12512 <ul>
12513 <li> minimum value of pointer-holding signed integer type
12514 <pre>
12516 <li> maximum value of pointer-holding signed integer type
12517 <!--page 271 -->
12518 <pre>
12520 <li> maximum value of pointer-holding unsigned integer type
12522 </ul>
12524 <h5><a name="7.18.2.5" href="#7.18.2.5">7.18.2.5 Limits of greatest-width integer types</a></h5>
12526 <ul>
12527 <li> minimum value of greatest-width signed integer type
12529 <li> maximum value of greatest-width signed integer type
12531 <li> maximum value of greatest-width unsigned integer type
12533 </ul>
12537 The following object-like macros<sup><a href="#note227"><b>227)</b></a></sup> specify the minimum and maximum limits of
12538 integer types corresponding to types defined in other standard headers.
12540 Each instance of these macros shall be replaced by a constant expression suitable for use
12541 in #if preprocessing directives, and this expression shall have the same type as would an
12542 expression that is an object of the corresponding type converted according to the integer
12543 promotions. Its implementation-defined value shall be equal to or greater in magnitude
12544 (absolute value) than the corresponding value given below, with the same sign. An
12545 implementation shall define only the macros corresponding to those typedef names it
12547 <ul>
12548 <li> limits of ptrdiff_t
12549 PTRDIFF_MIN -65535
12550 PTRDIFF_MAX +65535
12551 <li> limits of sig_atomic_t
12552 SIG_ATOMIC_MIN see below
12553 SIG_ATOMIC_MAX see below
12554 <li> limit of size_t
12555 SIZE_MAX 65535
12556 <li> limits of wchar_t
12560 <!--page 272 -->
12561 WCHAR_MIN see below
12562 WCHAR_MAX see below
12563 <li> limits of wint_t
12564 WINT_MIN see below
12565 WINT_MAX see below
12566 </ul>
12568 If sig_atomic_t (see <a href="#7.14">7.14</a>) is defined as a signed integer type, the value of
12569 SIG_ATOMIC_MIN shall be no greater than -127 and the value of SIG_ATOMIC_MAX
12570 shall be no less than 127; otherwise, sig_atomic_t is defined as an unsigned integer
12571 type, and the value of SIG_ATOMIC_MIN shall be 0 and the value of
12572 SIG_ATOMIC_MAX shall be no less than 255.
12574 If wchar_t (see <a href="#7.17">7.17</a>) is defined as a signed integer type, the value of WCHAR_MIN
12576 otherwise, wchar_t is defined as an unsigned integer type, and the value of
12577 WCHAR_MIN shall be 0 and the value of WCHAR_MAX shall be no less than 255.<sup><a href="#note229"><b>229)</b></a></sup>
12579 If wint_t (see <a href="#7.24">7.24</a>) is defined as a signed integer type, the value of WINT_MIN shall
12581 otherwise, wint_t is defined as an unsigned integer type, and the value of WINT_MIN
12585 <p><small><a name="note227" href="#note227">227)</a> C++ implementations should define these macros only when __STDC_LIMIT_MACROS is defined
12587 </small>
12588 <p><small><a name="note228" href="#note228">228)</a> A freestanding implementation need not provide all of these types.
12589 </small>
12590 <p><small><a name="note229" href="#note229">229)</a> The values WCHAR_MIN and WCHAR_MAX do not necessarily correspond to members of the extended
12591 character set.
12592 </small>
12596 The following function-like macros<sup><a href="#note230"><b>230)</b></a></sup> expand to integer constants suitable for
12597 initializing objects that have integer types corresponding to types defined in
12598 <a href="#7.18"><stdint.h></a>. Each macro name corresponds to a similar type name in <a href="#7.18.1.2">7.18.1.2</a> or
12601 The argument in any instance of these macros shall be an unsuffixed integer constant (as
12602 defined in <a href="#6.4.4.1">6.4.4.1</a>) with a value that does not exceed the limits for the corresponding type.
12604 Each invocation of one of these macros shall expand to an integer constant expression
12605 suitable for use in #if preprocessing directives. The type of the expression shall have
12606 the same type as would an expression of the corresponding type converted according to
12607 the integer promotions. The value of the expression shall be that of the argument.
12612 <!--page 273 -->
12615 <p><small><a name="note230" href="#note230">230)</a> C++ implementations should define these macros only when __STDC_CONSTANT_MACROS is
12617 </small>
12619 <h5><a name="7.18.4.1" href="#7.18.4.1">7.18.4.1 Macros for minimum-width integer constants</a></h5>
12621 The macro INTN_C(value) shall expand to an integer constant expression
12622 corresponding to the type int_leastN_t. The macro UINTN_C(value) shall expand
12623 to an integer constant expression corresponding to the type uint_leastN_t. For
12624 example, if uint_least64_t is a name for the type unsigned long long int,
12627 <h5><a name="7.18.4.2" href="#7.18.4.2">7.18.4.2 Macros for greatest-width integer constants</a></h5>
12629 The following macro expands to an integer constant expression having the value specified
12630 by its argument and the type intmax_t:
12631 <pre>
12632 INTMAX_C(value)</pre>
12633 The following macro expands to an integer constant expression having the value specified
12634 by its argument and the type uintmax_t:
12635 <!--page 274 -->
12636 <pre>
12637 UINTMAX_C(value)</pre>
12643 The header <a href="#7.19"><stdio.h></a> declares three types, several macros, and many functions for
12644 performing input and output.
12647 <pre>
12648 FILE</pre>
12649 which is an object type capable of recording all the information needed to control a
12650 stream, including its file position indicator, a pointer to its associated buffer (if any), an
12651 error indicator that records whether a read/write error has occurred, and an end-of-file
12652 indicator that records whether the end of the file has been reached; and
12653 <pre>
12654 fpos_t</pre>
12655 which is an object type other than an array type capable of recording all the information
12656 needed to specify uniquely every position within a file.
12659 <pre>
12660 _IOFBF
12661 _IOLBF
12662 _IONBF</pre>
12663 which expand to integer constant expressions with distinct values, suitable for use as the
12664 third argument to the setvbuf function;
12665 <pre>
12666 BUFSIZ</pre>
12667 which expands to an integer constant expression that is the size of the buffer used by the
12668 setbuf function;
12669 <pre>
12670 EOF</pre>
12671 which expands to an integer constant expression, with type int and a negative value, that
12672 is returned by several functions to indicate end-of-file, that is, no more input from a
12673 stream;
12674 <pre>
12675 FOPEN_MAX</pre>
12676 which expands to an integer constant expression that is the minimum number of files that
12677 the implementation guarantees can be open simultaneously;
12678 <pre>
12679 FILENAME_MAX</pre>
12680 which expands to an integer constant expression that is the size needed for an array of
12681 char large enough to hold the longest file name string that the implementation
12682 <!--page 275 -->
12684 <pre>
12685 L_tmpnam</pre>
12686 which expands to an integer constant expression that is the size needed for an array of
12687 char large enough to hold a temporary file name string generated by the tmpnam
12688 function;
12689 <pre>
12690 SEEK_CUR
12691 SEEK_END
12692 SEEK_SET</pre>
12693 which expand to integer constant expressions with distinct values, suitable for use as the
12694 third argument to the fseek function;
12695 <pre>
12696 TMP_MAX</pre>
12697 which expands to an integer constant expression that is the maximum number of unique
12698 file names that can be generated by the tmpnam function;
12699 <pre>
12700 stderr
12701 stdin
12702 stdout</pre>
12703 which are expressions of type ''pointer to FILE'' that point to the FILE objects
12704 associated, respectively, with the standard error, input, and output streams.
12706 The header <a href="#7.24"><wchar.h></a> declares a number of functions useful for wide character input
12707 and output. The wide character input/output functions described in that subclause
12708 provide operations analogous to most of those described here, except that the
12709 fundamental units internal to the program are wide characters. The external
12710 representation (in the file) is a sequence of ''generalized'' multibyte characters, as
12713 The input/output functions are given the following collective terms:
12714 <ul>
12715 <li> The wide character input functions -- those functions described in <a href="#7.24">7.24</a> that perform
12716 input into wide characters and wide strings: fgetwc, fgetws, getwc, getwchar,
12717 fwscanf, wscanf, vfwscanf, and vwscanf.
12718 <li> The wide character output functions -- those functions described in <a href="#7.24">7.24</a> that perform
12719 output from wide characters and wide strings: fputwc, fputws, putwc,
12720 putwchar, fwprintf, wprintf, vfwprintf, and vwprintf.
12723 <!--page 276 -->
12724 <li> The wide character input/output functions -- the union of the ungetwc function, the
12725 wide character input functions, and the wide character output functions.
12726 <li> The byte input/output functions -- those functions described in this subclause that
12727 perform input/output: fgetc, fgets, fprintf, fputc, fputs, fread,
12728 fscanf, fwrite, getc, getchar, gets, printf, putc, putchar, puts,
12729 scanf, ungetc, vfprintf, vfscanf, vprintf, and vscanf.
12730 </ul>
12731 <p><b> Forward references</b>: files (<a href="#7.19.3">7.19.3</a>), the fseek function (<a href="#7.19.9.2">7.19.9.2</a>), streams (<a href="#7.19.2">7.19.2</a>), the
12732 tmpnam function (<a href="#7.19.4.4">7.19.4.4</a>), <a href="#7.24"><wchar.h></a> (<a href="#7.24">7.24</a>).
12735 <p><small><a name="note231" href="#note231">231)</a> If the implementation imposes no practical limit on the length of file name strings, the value of
12736 FILENAME_MAX should instead be the recommended size of an array intended to hold a file name
12737 string. Of course, file name string contents are subject to other system-specific constraints; therefore
12738 all possible strings of length FILENAME_MAX cannot be expected to be opened successfully.
12739 </small>
12743 Input and output, whether to or from physical devices such as terminals and tape drives,
12744 or whether to or from files supported on structured storage devices, are mapped into
12745 logical data streams, whose properties are more uniform than their various inputs and
12746 outputs. Two forms of mapping are supported, for text streams and for binary
12749 A text stream is an ordered sequence of characters composed into lines, each line
12750 consisting of zero or more characters plus a terminating new-line character. Whether the
12751 last line requires a terminating new-line character is implementation-defined. Characters
12752 may have to be added, altered, or deleted on input and output to conform to differing
12753 conventions for representing text in the host environment. Thus, there need not be a one-
12754 to-one correspondence between the characters in a stream and those in the external
12755 representation. Data read in from a text stream will necessarily compare equal to the data
12756 that were earlier written out to that stream only if: the data consist only of printing
12757 characters and the control characters horizontal tab and new-line; no new-line character is
12758 immediately preceded by space characters; and the last character is a new-line character.
12759 Whether space characters that are written out immediately before a new-line character
12760 appear when read in is implementation-defined.
12762 A binary stream is an ordered sequence of characters that can transparently record
12763 internal data. Data read in from a binary stream shall compare equal to the data that were
12764 earlier written out to that stream, under the same implementation. Such a stream may,
12765 however, have an implementation-defined number of null characters appended to the end
12766 of the stream.
12768 Each stream has an orientation. After a stream is associated with an external file, but
12769 before any operations are performed on it, the stream is without orientation. Once a wide
12770 character input/output function has been applied to a stream without orientation, the
12773 <!--page 277 -->
12774 stream becomes a wide-oriented stream. Similarly, once a byte input/output function has
12775 been applied to a stream without orientation, the stream becomes a byte-oriented stream.
12776 Only a call to the freopen function or the fwide function can otherwise alter the
12777 orientation of a stream. (A successful call to freopen removes any orientation.)<sup><a href="#note233"><b>233)</b></a></sup>
12779 Byte input/output functions shall not be applied to a wide-oriented stream and wide
12780 character input/output functions shall not be applied to a byte-oriented stream. The
12781 remaining stream operations do not affect, and are not affected by, a stream's orientation,
12782 except for the following additional restrictions:
12783 <ul>
12784 <li> Binary wide-oriented streams have the file-positioning restrictions ascribed to both
12785 text and binary streams.
12786 <li> For wide-oriented streams, after a successful call to a file-positioning function that
12787 leaves the file position indicator prior to the end-of-file, a wide character output
12788 function can overwrite a partial multibyte character; any file contents beyond the
12789 byte(s) written are henceforth indeterminate.
12790 </ul>
12792 Each wide-oriented stream has an associated mbstate_t object that stores the current
12793 parse state of the stream. A successful call to fgetpos stores a representation of the
12794 value of this mbstate_t object as part of the value of the fpos_t object. A later
12795 successful call to fsetpos using the same stored fpos_t value restores the value of
12796 the associated mbstate_t object as well as the position within the controlled stream.
12797 Environmental limits
12799 An implementation shall support text files with lines containing at least 254 characters,
12800 including the terminating new-line character. The value of the macro BUFSIZ shall be at
12801 least 256.
12802 <p><b> Forward references</b>: the freopen function (<a href="#7.19.5.4">7.19.5.4</a>), the fwide function (<a href="#7.24.3.5">7.24.3.5</a>),
12803 mbstate_t (<a href="#7.25.1">7.25.1</a>), the fgetpos function (<a href="#7.19.9.1">7.19.9.1</a>), the fsetpos function
12809 <!--page 278 -->
12812 <p><small><a name="note232" href="#note232">232)</a> An implementation need not distinguish between text streams and binary streams. In such an
12813 implementation, there need be no new-line characters in a text stream nor any limit to the length of a
12814 line.
12815 </small>
12816 <p><small><a name="note233" href="#note233">233)</a> The three predefined streams stdin, stdout, and stderr are unoriented at program startup.
12817 </small>
12821 A stream is associated with an external file (which may be a physical device) by opening
12822 a file, which may involve creating a new file. Creating an existing file causes its former
12823 contents to be discarded, if necessary. If a file can support positioning requests (such as a
12824 disk file, as opposed to a terminal), then a file position indicator associated with the
12825 stream is positioned at the start (character number zero) of the file, unless the file is
12826 opened with append mode in which case it is implementation-defined whether the file
12827 position indicator is initially positioned at the beginning or the end of the file. The file
12828 position indicator is maintained by subsequent reads, writes, and positioning requests, to
12829 facilitate an orderly progression through the file.
12831 Binary files are not truncated, except as defined in <a href="#7.19.5.3">7.19.5.3</a>. Whether a write on a text
12832 stream causes the associated file to be truncated beyond that point is implementation-
12833 defined.
12835 When a stream is unbuffered, characters are intended to appear from the source or at the
12836 destination as soon as possible. Otherwise characters may be accumulated and
12837 transmitted to or from the host environment as a block. When a stream is fully buffered,
12838 characters are intended to be transmitted to or from the host environment as a block when
12839 a buffer is filled. When a stream is line buffered, characters are intended to be
12840 transmitted to or from the host environment as a block when a new-line character is
12841 encountered. Furthermore, characters are intended to be transmitted as a block to the host
12842 environment when a buffer is filled, when input is requested on an unbuffered stream, or
12843 when input is requested on a line buffered stream that requires the transmission of
12844 characters from the host environment. Support for these characteristics is
12845 implementation-defined, and may be affected via the setbuf and setvbuf functions.
12847 A file may be disassociated from a controlling stream by closing the file. Output streams
12848 are flushed (any unwritten buffer contents are transmitted to the host environment) before
12849 the stream is disassociated from the file. The value of a pointer to a FILE object is
12850 indeterminate after the associated file is closed (including the standard text streams).
12851 Whether a file of zero length (on which no characters have been written by an output
12852 stream) actually exists is implementation-defined.
12854 The file may be subsequently reopened, by the same or another program execution, and
12855 its contents reclaimed or modified (if it can be repositioned at its start). If the main
12856 function returns to its original caller, or if the exit function is called, all open files are
12857 closed (hence all output streams are flushed) before program termination. Other paths to
12858 program termination, such as calling the abort function, need not close all files
12859 properly.
12861 The address of the FILE object used to control a stream may be significant; a copy of a
12862 FILE object need not serve in place of the original.
12863 <!--page 279 -->
12865 At program startup, three text streams are predefined and need not be opened explicitly
12866 <ul>
12867 <li> standard input (for reading conventional input), standard output (for writing
12868 </ul>
12869 conventional output), and standard error (for writing diagnostic output). As initially
12870 opened, the standard error stream is not fully buffered; the standard input and standard
12871 output streams are fully buffered if and only if the stream can be determined not to refer
12872 to an interactive device.
12874 Functions that open additional (nontemporary) files require a file name, which is a string.
12875 The rules for composing valid file names are implementation-defined. Whether the same
12876 file can be simultaneously open multiple times is also implementation-defined.
12878 Although both text and binary wide-oriented streams are conceptually sequences of wide
12879 characters, the external file associated with a wide-oriented stream is a sequence of
12880 multibyte characters, generalized as follows:
12881 <ul>
12882 <li> Multibyte encodings within files may contain embedded null bytes (unlike multibyte
12883 encodings valid for use internal to the program).
12884 <li> A file need not begin nor end in the initial shift state.<sup><a href="#note234"><b>234)</b></a></sup>
12885 </ul>
12887 Moreover, the encodings used for multibyte characters may differ among files. Both the
12888 nature and choice of such encodings are implementation-defined.
12890 The wide character input functions read multibyte characters from the stream and convert
12891 them to wide characters as if they were read by successive calls to the fgetwc function.
12892 Each conversion occurs as if by a call to the mbrtowc function, with the conversion state
12893 described by the stream's own mbstate_t object. The byte input functions read
12894 characters from the stream as if by successive calls to the fgetc function.
12896 The wide character output functions convert wide characters to multibyte characters and
12897 write them to the stream as if they were written by successive calls to the fputwc
12898 function. Each conversion occurs as if by a call to the wcrtomb function, with the
12899 conversion state described by the stream's own mbstate_t object. The byte output
12900 functions write characters to the stream as if by successive calls to the fputc function.
12902 In some cases, some of the byte input/output functions also perform conversions between
12903 multibyte characters and wide characters. These conversions also occur as if by calls to
12904 the mbrtowc and wcrtomb functions.
12906 An encoding error occurs if the character sequence presented to the underlying
12907 mbrtowc function does not form a valid (generalized) multibyte character, or if the code
12908 value passed to the underlying wcrtomb does not correspond to a valid (generalized)
12911 <!--page 280 -->
12912 multibyte character. The wide character input/output functions and the byte input/output
12913 functions store the value of the macro EILSEQ in errno if and only if an encoding error
12914 occurs.
12915 Environmental limits
12917 The value of FOPEN_MAX shall be at least eight, including the three standard text
12918 streams.
12919 <p><b> Forward references</b>: the exit function (<a href="#7.20.4.3">7.20.4.3</a>), the fgetc function (<a href="#7.19.7.1">7.19.7.1</a>), the
12920 fopen function (<a href="#7.19.5.3">7.19.5.3</a>), the fputc function (<a href="#7.19.7.3">7.19.7.3</a>), the setbuf function
12921 (<a href="#7.19.5.5">7.19.5.5</a>), the setvbuf function (<a href="#7.19.5.6">7.19.5.6</a>), the fgetwc function (<a href="#7.24.3.1">7.24.3.1</a>), the
12922 fputwc function (<a href="#7.24.3.3">7.24.3.3</a>), conversion state (<a href="#7.24.6">7.24.6</a>), the mbrtowc function
12923 (<a href="#7.24.6.3.2">7.24.6.3.2</a>), the wcrtomb function (<a href="#7.24.6.3.3">7.24.6.3.3</a>).
12926 <p><small><a name="note234" href="#note234">234)</a> Setting the file position indicator to end-of-file, as with fseek(file, 0, SEEK_END), has
12927 undefined behavior for a binary stream (because of possible trailing null characters) or for any stream
12928 with state-dependent encoding that does not assuredly end in the initial shift state.
12929 </small>
12936 <pre>
12938 int remove(const char *filename);</pre>
12941 The remove function causes the file whose name is the string pointed to by filename
12942 to be no longer accessible by that name. A subsequent attempt to open that file using that
12943 name will fail, unless it is created anew. If the file is open, the behavior of the remove
12944 function is implementation-defined.
12947 The remove function returns zero if the operation succeeds, nonzero if it fails.
12952 <pre>
12954 int rename(const char *old, const char *new);</pre>
12957 The rename function causes the file whose name is the string pointed to by old to be
12958 henceforth known by the name given by the string pointed to by new. The file named
12959 old is no longer accessible by that name. If a file named by the string pointed to by new
12960 exists prior to the call to the rename function, the behavior is implementation-defined.
12961 <!--page 281 -->
12964 The rename function returns zero if the operation succeeds, nonzero if it fails,<sup><a href="#note235"><b>235)</b></a></sup> in
12965 which case if the file existed previously it is still known by its original name.
12968 <p><small><a name="note235" href="#note235">235)</a> Among the reasons the implementation may cause the rename function to fail are that the file is open
12969 or that it is necessary to copy its contents to effectuate its renaming.
12970 </small>
12975 <pre>
12977 FILE *tmpfile(void);</pre>
12980 The tmpfile function creates a temporary binary file that is different from any other
12981 existing file and that will automatically be removed when it is closed or at program
12982 termination. If the program terminates abnormally, whether an open temporary file is
12983 removed is implementation-defined. The file is opened for update with "wb+" mode.
12984 Recommended practice
12986 It should be possible to open at least TMP_MAX temporary files during the lifetime of the
12987 program (this limit may be shared with tmpnam) and there should be no limit on the
12988 number simultaneously open other than this limit and any limit on the number of open
12989 files (FOPEN_MAX).
12992 The tmpfile function returns a pointer to the stream of the file that it created. If the file
12993 cannot be created, the tmpfile function returns a null pointer.
12999 <pre>
13001 char *tmpnam(char *s);</pre>
13004 The tmpnam function generates a string that is a valid file name and that is not the same
13005 as the name of an existing file.<sup><a href="#note236"><b>236)</b></a></sup> The function is potentially capable of generating
13008 <!--page 282 -->
13009 TMP_MAX different strings, but any or all of them may already be in use by existing files
13010 and thus not be suitable return values.
13012 The tmpnam function generates a different string each time it is called.
13014 The implementation shall behave as if no library function calls the tmpnam function.
13017 If no suitable string can be generated, the tmpnam function returns a null pointer.
13018 Otherwise, if the argument is a null pointer, the tmpnam function leaves its result in an
13019 internal static object and returns a pointer to that object (subsequent calls to the tmpnam
13020 function may modify the same object). If the argument is not a null pointer, it is assumed
13021 to point to an array of at least L_tmpnam chars; the tmpnam function writes its result
13022 in that array and returns the argument as its value.
13023 Environmental limits
13025 The value of the macro TMP_MAX shall be at least 25.
13028 <p><small><a name="note236" href="#note236">236)</a> Files created using strings generated by the tmpnam function are temporary only in the sense that
13029 their names should not collide with those generated by conventional naming rules for the
13030 implementation. It is still necessary to use the remove function to remove such files when their use
13031 is ended, and before program termination.
13032 </small>
13039 <pre>
13041 int fclose(FILE *stream);</pre>
13044 A successful call to the fclose function causes the stream pointed to by stream to be
13045 flushed and the associated file to be closed. Any unwritten buffered data for the stream
13046 are delivered to the host environment to be written to the file; any unread buffered data
13047 are discarded. Whether or not the call succeeds, the stream is disassociated from the file
13048 and any buffer set by the setbuf or setvbuf function is disassociated from the stream
13049 (and deallocated if it was automatically allocated).
13052 The fclose function returns zero if the stream was successfully closed, or EOF if any
13053 errors were detected.
13058 <!--page 283 -->
13059 <pre>
13061 int fflush(FILE *stream);</pre>
13064 If stream points to an output stream or an update stream in which the most recent
13065 operation was not input, the fflush function causes any unwritten data for that stream
13066 to be delivered to the host environment to be written to the file; otherwise, the behavior is
13067 undefined.
13069 If stream is a null pointer, the fflush function performs this flushing action on all
13070 streams for which the behavior is defined above.
13073 The fflush function sets the error indicator for the stream and returns EOF if a write
13074 error occurs, otherwise it returns zero.
13080 <pre>
13082 FILE *fopen(const char * restrict filename,
13083 const char * restrict mode);</pre>
13086 The fopen function opens the file whose name is the string pointed to by filename,
13087 and associates a stream with it.
13089 The argument mode points to a string. If the string is one of the following, the file is
13090 open in the indicated mode. Otherwise, the behavior is undefined.<sup><a href="#note237"><b>237)</b></a></sup>
13091 r open text file for reading
13092 w truncate to zero length or create text file for writing
13093 a append; open or create text file for writing at end-of-file
13094 rb open binary file for reading
13095 wb truncate to zero length or create binary file for writing
13096 ab append; open or create binary file for writing at end-of-file
13097 r+ open text file for update (reading and writing)
13098 w+ truncate to zero length or create text file for update
13099 a+ append; open or create text file for update, writing at end-of-file
13104 <!--page 284 -->
13105 r+b or rb+ open binary file for update (reading and writing)
13106 w+b or wb+ truncate to zero length or create binary file for update
13107 a+b or ab+ append; open or create binary file for update, writing at end-of-file
13109 Opening a file with read mode ('r' as the first character in the mode argument) fails if
13110 the file does not exist or cannot be read.
13112 Opening a file with append mode ('a' as the first character in the mode argument)
13113 causes all subsequent writes to the file to be forced to the then current end-of-file,
13114 regardless of intervening calls to the fseek function. In some implementations, opening
13115 a binary file with append mode ('b' as the second or third character in the above list of
13116 mode argument values) may initially position the file position indicator for the stream
13117 beyond the last data written, because of null character padding.
13119 When a file is opened with update mode ('+' as the second or third character in the
13120 above list of mode argument values), both input and output may be performed on the
13121 associated stream. However, output shall not be directly followed by input without an
13122 intervening call to the fflush function or to a file positioning function (fseek,
13123 fsetpos, or rewind), and input shall not be directly followed by output without an
13124 intervening call to a file positioning function, unless the input operation encounters end-
13125 of-file. Opening (or creating) a text file with update mode may instead open (or create) a
13126 binary stream in some implementations.
13128 When opened, a stream is fully buffered if and only if it can be determined not to refer to
13129 an interactive device. The error and end-of-file indicators for the stream are cleared.
13132 The fopen function returns a pointer to the object controlling the stream. If the open
13133 operation fails, fopen returns a null pointer.
13137 <p><small><a name="note237" href="#note237">237)</a> If the string begins with one of the above sequences, the implementation might choose to ignore the
13138 remaining characters, or it might use them to select different kinds of a file (some of which might not
13140 </small>
13145 <pre>
13147 FILE *freopen(const char * restrict filename,
13148 const char * restrict mode,
13149 FILE * restrict stream);</pre>
13152 The freopen function opens the file whose name is the string pointed to by filename
13153 and associates the stream pointed to by stream with it. The mode argument is used just
13154 <!--page 285 -->
13157 If filename is a null pointer, the freopen function attempts to change the mode of
13158 the stream to that specified by mode, as if the name of the file currently associated with
13159 the stream had been used. It is implementation-defined which changes of mode are
13160 permitted (if any), and under what circumstances.
13162 The freopen function first attempts to close any file that is associated with the specified
13163 stream. Failure to close the file is ignored. The error and end-of-file indicators for the
13164 stream are cleared.
13167 The freopen function returns a null pointer if the open operation fails. Otherwise,
13168 freopen returns the value of stream.
13171 <p><small><a name="note238" href="#note238">238)</a> The primary use of the freopen function is to change the file associated with a standard text stream
13172 (stderr, stdin, or stdout), as those identifiers need not be modifiable lvalues to which the value
13173 returned by the fopen function may be assigned.
13174 </small>
13179 <pre>
13181 void setbuf(FILE * restrict stream,
13182 char * restrict buf);</pre>
13185 Except that it returns no value, the setbuf function is equivalent to the setvbuf
13186 function invoked with the values _IOFBF for mode and BUFSIZ for size, or (if buf
13187 is a null pointer), with the value _IONBF for mode.
13190 The setbuf function returns no value.
13196 <pre>
13198 int setvbuf(FILE * restrict stream,
13199 char * restrict buf,
13200 int mode, size_t size);</pre>
13205 <!--page 286 -->
13208 The setvbuf function may be used only after the stream pointed to by stream has
13209 been associated with an open file and before any other operation (other than an
13210 unsuccessful call to setvbuf) is performed on the stream. The argument mode
13211 determines how stream will be buffered, as follows: _IOFBF causes input/output to be
13212 fully buffered; _IOLBF causes input/output to be line buffered; _IONBF causes
13213 input/output to be unbuffered. If buf is not a null pointer, the array it points to may be
13214 used instead of a buffer allocated by the setvbuf function<sup><a href="#note239"><b>239)</b></a></sup> and the argument size
13215 specifies the size of the array; otherwise, size may determine the size of a buffer
13216 allocated by the setvbuf function. The contents of the array at any time are
13217 indeterminate.
13220 The setvbuf function returns zero on success, or nonzero if an invalid value is given
13221 for mode or if the request cannot be honored.
13224 <p><small><a name="note239" href="#note239">239)</a> The buffer has to have a lifetime at least as great as the open stream, so the stream should be closed
13225 before a buffer that has automatic storage duration is deallocated upon block exit.
13226 </small>
13230 The formatted input/output functions shall behave as if there is a sequence point after the
13234 <p><small><a name="note240" href="#note240">240)</a> The fprintf functions perform writes to memory for the %n specifier.
13235 </small>
13240 <pre>
13242 int fprintf(FILE * restrict stream,
13243 const char * restrict format, ...);</pre>
13246 The fprintf function writes output to the stream pointed to by stream, under control
13247 of the string pointed to by format that specifies how subsequent arguments are
13248 converted for output. If there are insufficient arguments for the format, the behavior is
13249 undefined. If the format is exhausted while arguments remain, the excess arguments are
13250 evaluated (as always) but are otherwise ignored. The fprintf function returns when
13251 the end of the format string is encountered.
13253 The format shall be a multibyte character sequence, beginning and ending in its initial
13254 shift state. The format is composed of zero or more directives: ordinary multibyte
13255 characters (not %), which are copied unchanged to the output stream; and conversion
13258 <!--page 287 -->
13259 specifications, each of which results in fetching zero or more subsequent arguments,
13260 converting them, if applicable, according to the corresponding conversion specifier, and
13261 then writing the result to the output stream.
13263 Each conversion specification is introduced by the character %. After the %, the following
13264 appear in sequence:
13265 <ul>
13266 <li> Zero or more flags (in any order) that modify the meaning of the conversion
13267 specification.
13268 <li> An optional minimum field width. If the converted value has fewer characters than the
13269 field width, it is padded with spaces (by default) on the left (or right, if the left
13270 adjustment flag, described later, has been given) to the field width. The field width
13271 takes the form of an asterisk * (described later) or a nonnegative decimal integer.<sup><a href="#note241"><b>241)</b></a></sup>
13272 <li> An optional precision that gives the minimum number of digits to appear for the d, i,
13273 o, u, x, and X conversions, the number of digits to appear after the decimal-point
13274 character for a, A, e, E, f, and F conversions, the maximum number of significant
13275 digits for the g and G conversions, or the maximum number of bytes to be written for
13276 s conversions. The precision takes the form of a period (.) followed either by an
13277 asterisk * (described later) or by an optional decimal integer; if only the period is
13278 specified, the precision is taken as zero. If a precision appears with any other
13279 conversion specifier, the behavior is undefined.
13280 <li> An optional length modifier that specifies the size of the argument.
13281 <li> A conversion specifier character that specifies the type of conversion to be applied.
13282 </ul>
13284 As noted above, a field width, or precision, or both, may be indicated by an asterisk. In
13285 this case, an int argument supplies the field width or precision. The arguments
13286 specifying field width, or precision, or both, shall appear (in that order) before the
13287 argument (if any) to be converted. A negative field width argument is taken as a - flag
13288 followed by a positive field width. A negative precision argument is taken as if the
13289 precision were omitted.
13291 The flag characters and their meanings are:
13292 - The result of the conversion is left-justified within the field. (It is right-justified if
13293 <pre>
13294 this flag is not specified.)</pre>
13295 + The result of a signed conversion always begins with a plus or minus sign. (It
13296 <pre>
13297 begins with a sign only when a negative value is converted if this flag is not</pre>
13302 <!--page 288 -->
13303 <pre>
13305 space If the first character of a signed conversion is not a sign, or if a signed conversion
13306 <pre>
13307 results in no characters, a space is prefixed to the result. If the space and + flags
13308 both appear, the space flag is ignored.</pre>
13309 # The result is converted to an ''alternative form''. For o conversion, it increases
13310 <pre>
13311 the precision, if and only if necessary, to force the first digit of the result to be a
13314 and G conversions, the result of converting a floating-point number always
13315 contains a decimal-point character, even if no digits follow it. (Normally, a
13316 decimal-point character appears in the result of these conversions only if a digit
13317 follows it.) For g and G conversions, trailing zeros are not removed from the
13318 result. For other conversions, the behavior is undefined.</pre>
13319 0 For d, i, o, u, x, X, a, A, e, E, f, F, g, and G conversions, leading zeros
13321 <pre>
13322 (following any indication of sign or base) are used to pad to the field width rather
13323 than performing space padding, except when converting an infinity or NaN. If the
13325 conversions, if a precision is specified, the 0 flag is ignored. For other
13326 conversions, the behavior is undefined.</pre>
13327 The length modifiers and their meanings are:
13328 hh Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
13329 <pre>
13330 signed char or unsigned char argument (the argument will have
13331 been promoted according to the integer promotions, but its value shall be
13332 converted to signed char or unsigned char before printing); or that
13333 a following n conversion specifier applies to a pointer to a signed char
13334 argument.</pre>
13335 h Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
13336 <pre>
13337 short int or unsigned short int argument (the argument will
13338 have been promoted according to the integer promotions, but its value shall
13339 be converted to short int or unsigned short int before printing);
13340 or that a following n conversion specifier applies to a pointer to a short
13341 int argument.</pre>
13342 l (ell) Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
13343 <pre>
13344 long int or unsigned long int argument; that a following n
13345 conversion specifier applies to a pointer to a long int argument; that a</pre>
13347 <!--page 289 -->
13348 <pre>
13349 following c conversion specifier applies to a wint_t argument; that a
13350 following s conversion specifier applies to a pointer to a wchar_t
13351 argument; or has no effect on a following a, A, e, E, f, F, g, or G conversion
13352 specifier.</pre>
13353 ll (ell-ell) Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
13354 <pre>
13355 long long int or unsigned long long int argument; or that a
13356 following n conversion specifier applies to a pointer to a long long int
13357 argument.</pre>
13358 j Specifies that a following d, i, o, u, x, or X conversion specifier applies to
13359 <pre>
13360 an intmax_t or uintmax_t argument; or that a following n conversion
13361 specifier applies to a pointer to an intmax_t argument.</pre>
13362 z Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
13363 <pre>
13364 size_t or the corresponding signed integer type argument; or that a
13365 following n conversion specifier applies to a pointer to a signed integer type
13366 corresponding to size_t argument.</pre>
13367 t Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
13368 <pre>
13369 ptrdiff_t or the corresponding unsigned integer type argument; or that a
13370 following n conversion specifier applies to a pointer to a ptrdiff_t
13371 argument.</pre>
13372 L Specifies that a following a, A, e, E, f, F, g, or G conversion specifier
13373 <pre>
13374 applies to a long double argument.</pre>
13375 If a length modifier appears with any conversion specifier other than as specified above,
13376 the behavior is undefined.
13378 The conversion specifiers and their meanings are:
13379 d,i The int argument is converted to signed decimal in the style [-]dddd. The
13380 <pre>
13381 precision specifies the minimum number of digits to appear; if the value
13382 being converted can be represented in fewer digits, it is expanded with
13383 leading zeros. The default precision is 1. The result of converting a zero
13384 value with a precision of zero is no characters.</pre>
13385 o,u,x,X The unsigned int argument is converted to unsigned octal (o), unsigned
13386 <!--page 290 -->
13387 <pre>
13388 decimal (u), or unsigned hexadecimal notation (x or X) in the style dddd; the
13389 letters abcdef are used for x conversion and the letters ABCDEF for X
13390 conversion. The precision specifies the minimum number of digits to appear;
13391 if the value being converted can be represented in fewer digits, it is expanded
13392 with leading zeros. The default precision is 1. The result of converting a
13393 zero value with a precision of zero is no characters.</pre>
13394 f,F A double argument representing a floating-point number is converted to
13395 <pre>
13396 decimal notation in the style [-]ddd.ddd, where the number of digits after
13397 the decimal-point character is equal to the precision specification. If the
13398 precision is missing, it is taken as 6; if the precision is zero and the # flag is
13399 not specified, no decimal-point character appears. If a decimal-point
13400 character appears, at least one digit appears before it. The value is rounded to
13401 the appropriate number of digits.
13402 A double argument representing an infinity is converted in one of the styles
13403 [-]inf or [-]infinity -- which style is implementation-defined. A
13404 double argument representing a NaN is converted in one of the styles
13405 [-]nan or [-]nan(n-char-sequence) -- which style, and the meaning of
13406 any n-char-sequence, is implementation-defined. The F conversion specifier
13407 produces INF, INFINITY, or NAN instead of inf, infinity, or nan,
13409 e,E A double argument representing a floating-point number is converted in the
13410 <pre>
13411 style [-]d.ddd e(+-)dd, where there is one digit (which is nonzero if the
13412 argument is nonzero) before the decimal-point character and the number of
13413 digits after it is equal to the precision; if the precision is missing, it is taken as
13414 6; if the precision is zero and the # flag is not specified, no decimal-point
13415 character appears. The value is rounded to the appropriate number of digits.
13416 The E conversion specifier produces a number with E instead of e
13417 introducing the exponent. The exponent always contains at least two digits,
13418 and only as many more digits as necessary to represent the exponent. If the
13419 value is zero, the exponent is zero.
13420 A double argument representing an infinity or NaN is converted in the style
13421 of an f or F conversion specifier.</pre>
13422 g,G A double argument representing a floating-point number is converted in
13423 <pre>
13424 style f or e (or in style F or E in the case of a G conversion specifier),
13425 depending on the value converted and the precision. Let P equal the
13427 Then, if a conversion with style E would have an exponent of X :
13429 P - (X + 1).
13430 -- otherwise, the conversion is with style e (or E) and precision P - 1.
13431 Finally, unless the # flag is used, any trailing zeros are removed from the</pre>
13433 <!--page 291 -->
13434 <pre>
13435 fractional portion of the result and the decimal-point character is removed if
13436 there is no fractional portion remaining.
13437 A double argument representing an infinity or NaN is converted in the style
13438 of an f or F conversion specifier.</pre>
13439 a,A A double argument representing a floating-point number is converted in the
13440 <pre>
13441 style [-]0xh.hhhh p(+-)d, where there is one hexadecimal digit (which is
13442 nonzero if the argument is a normalized floating-point number and is
13443 otherwise unspecified) before the decimal-point character<sup><a href="#note244"><b>244)</b></a></sup> and the number
13444 of hexadecimal digits after it is equal to the precision; if the precision is
13445 missing and FLT_RADIX is a power of 2, then the precision is sufficient for
13446 an exact representation of the value; if the precision is missing and
13447 FLT_RADIX is not a power of 2, then the precision is sufficient to
13448 distinguish<sup><a href="#note245"><b>245)</b></a></sup> values of type double, except that trailing zeros may be
13449 omitted; if the precision is zero and the # flag is not specified, no decimal-
13450 point character appears. The letters abcdef are used for a conversion and
13451 the letters ABCDEF for A conversion. The A conversion specifier produces a
13452 number with X and P instead of x and p. The exponent always contains at
13453 least one digit, and only as many more digits as necessary to represent the
13454 decimal exponent of 2. If the value is zero, the exponent is zero.
13455 A double argument representing an infinity or NaN is converted in the style
13456 of an f or F conversion specifier.</pre>
13457 c If no l length modifier is present, the int argument is converted to an
13458 <pre>
13459 unsigned char, and the resulting character is written.
13460 If an l length modifier is present, the wint_t argument is converted as if by
13461 an ls conversion specification with no precision and an argument that points
13462 to the initial element of a two-element array of wchar_t, the first element
13463 containing the wint_t argument to the lc conversion specification and the
13464 second a null wide character.</pre>
13465 s If no l length modifier is present, the argument shall be a pointer to the initial
13466 <pre>
13467 element of an array of character type.<sup><a href="#note246"><b>246)</b></a></sup> Characters from the array are</pre>
13470 <!--page 292 -->
13471 <pre>
13472 written up to (but not including) the terminating null character. If the
13473 precision is specified, no more than that many bytes are written. If the
13474 precision is not specified or is greater than the size of the array, the array shall
13475 contain a null character.
13476 If an l length modifier is present, the argument shall be a pointer to the initial
13477 element of an array of wchar_t type. Wide characters from the array are
13478 converted to multibyte characters (each as if by a call to the wcrtomb
13479 function, with the conversion state described by an mbstate_t object
13480 initialized to zero before the first wide character is converted) up to and
13481 including a terminating null wide character. The resulting multibyte
13482 characters are written up to (but not including) the terminating null character
13483 (byte). If no precision is specified, the array shall contain a null wide
13484 character. If a precision is specified, no more than that many bytes are
13485 written (including shift sequences, if any), and the array shall contain a null
13486 wide character if, to equal the multibyte character sequence length given by
13487 the precision, the function would need to access a wide character one past the
13488 end of the array. In no case is a partial multibyte character written.<sup><a href="#note247"><b>247)</b></a></sup></pre>
13489 p The argument shall be a pointer to void. The value of the pointer is
13490 <pre>
13491 converted to a sequence of printing characters, in an implementation-defined
13492 manner.</pre>
13493 n The argument shall be a pointer to signed integer into which is written the
13494 <pre>
13495 number of characters written to the output stream so far by this call to
13496 fprintf. No argument is converted, but one is consumed. If the conversion
13497 specification includes any flags, a field width, or a precision, the behavior is
13498 undefined.</pre>
13499 % A % character is written. No argument is converted. The complete
13501 <pre>
13502 conversion specification shall be %%.</pre>
13503 If a conversion specification is invalid, the behavior is undefined.<sup><a href="#note248"><b>248)</b></a></sup> If any argument is
13504 not the correct type for the corresponding conversion specification, the behavior is
13505 undefined.
13507 In no case does a nonexistent or small field width cause truncation of a field; if the result
13508 of a conversion is wider than the field width, the field is expanded to contain the
13509 conversion result.
13514 <!--page 293 -->
13516 For a and A conversions, if FLT_RADIX is a power of 2, the value is correctly rounded
13517 to a hexadecimal floating number with the given precision.
13518 Recommended practice
13520 For a and A conversions, if FLT_RADIX is not a power of 2 and the result is not exactly
13521 representable in the given precision, the result should be one of the two adjacent numbers
13522 in hexadecimal floating style with the given precision, with the extra stipulation that the
13523 error should have a correct sign for the current rounding direction.
13525 For e, E, f, F, g, and G conversions, if the number of significant decimal digits is at most
13526 DECIMAL_DIG, then the result should be correctly rounded.<sup><a href="#note249"><b>249)</b></a></sup> If the number of
13527 significant decimal digits is more than DECIMAL_DIG but the source value is exactly
13528 representable with DECIMAL_DIG digits, then the result should be an exact
13529 representation with trailing zeros. Otherwise, the source value is bounded by two
13530 adjacent decimal strings L < U, both having DECIMAL_DIG significant digits; the value
13531 of the resultant decimal string D should satisfy L <= D <= U, with the extra stipulation that
13532 the error should have a correct sign for the current rounding direction.
13535 The fprintf function returns the number of characters transmitted, or a negative value
13536 if an output or encoding error occurred.
13537 Environmental limits
13539 The number of characters that can be produced by any single conversion shall be at least
13540 4095.
13542 EXAMPLE 1 To print a date and time in the form ''Sunday, July 3, 10:02'' followed by pi to five decimal
13543 places:
13544 <pre>
13547 /* ... */
13548 char *weekday, *month; // pointers to strings
13549 int day, hour, min;
13550 fprintf(stdout, "%s, %s %d, %.2d:%.2d\n",
13551 weekday, month, day, hour, min);
13555 EXAMPLE 2 In this example, multibyte characters do not have a state-dependent encoding, and the
13556 members of the extended character set that consist of more than one byte each consist of exactly two bytes,
13557 the first of which is denoted here by a and the second by an uppercase letter.
13562 <!--page 294 -->
13564 Given the following wide string with length seven,
13565 <pre>
13567 the seven calls
13568 <pre>
13569 fprintf(stdout, "|1234567890123|\n");
13570 fprintf(stdout, "|%13ls|\n", wstr);
13571 fprintf(stdout, "|%-13.9ls|\n", wstr);
13572 fprintf(stdout, "|%13.10ls|\n", wstr);
13573 fprintf(stdout, "|%13.11ls|\n", wstr);
13576 will print the following seven lines:
13577 <pre>
13578 |1234567890123|
13579 | X Yabc Z W|
13580 | X Yabc Z |
13581 | X Yabc Z|
13582 | X Yabc Z W|
13583 | abc Z W|
13584 | Z|</pre>
13586 <p><b> Forward references</b>: conversion state (<a href="#7.24.6">7.24.6</a>), the wcrtomb function (<a href="#7.24.6.3.3">7.24.6.3.3</a>).
13589 <p><small><a name="note241" href="#note241">241)</a> Note that 0 is taken as a flag, not as the beginning of a field width.
13590 </small>
13591 <p><small><a name="note242" href="#note242">242)</a> The results of all floating conversions of a negative zero, and of negative values that round to zero,
13592 include a minus sign.
13593 </small>
13594 <p><small><a name="note243" href="#note243">243)</a> When applied to infinite and NaN values, the -, +, and space flag characters have their usual meaning;
13595 the # and 0 flag characters have no effect.
13596 </small>
13597 <p><small><a name="note244" href="#note244">244)</a> Binary implementations can choose the hexadecimal digit to the left of the decimal-point character so
13598 that subsequent digits align to nibble (4-bit) boundaries.
13599 </small>
13600 <p><small><a name="note245" href="#note245">245)</a> The precision p is sufficient to distinguish values of the source type if 16 p-1 > b n where b is
13601 FLT_RADIX and n is the number of base-b digits in the significand of the source type. A smaller p
13602 might suffice depending on the implementation's scheme for determining the digit to the left of the
13603 decimal-point character.
13604 </small>
13605 <p><small><a name="note246" href="#note246">246)</a> No special provisions are made for multibyte characters.
13606 </small>
13607 <p><small><a name="note247" href="#note247">247)</a> Redundant shift sequences may result if multibyte characters have a state-dependent encoding.
13608 </small>
13609 <p><small><a name="note248" href="#note248">248)</a> See ''future library directions'' (<a href="#7.26.9">7.26.9</a>).
13610 </small>
13611 <p><small><a name="note249" href="#note249">249)</a> For binary-to-decimal conversion, the result format's values are the numbers representable with the
13612 given format specifier. The number of significant digits is determined by the format specifier, and in
13613 the case of fixed-point conversion by the source value as well.
13614 </small>
13619 <pre>
13621 int fscanf(FILE * restrict stream,
13622 const char * restrict format, ...);</pre>
13625 The fscanf function reads input from the stream pointed to by stream, under control
13626 of the string pointed to by format that specifies the admissible input sequences and how
13627 they are to be converted for assignment, using subsequent arguments as pointers to the
13628 objects to receive the converted input. If there are insufficient arguments for the format,
13629 the behavior is undefined. If the format is exhausted while arguments remain, the excess
13630 arguments are evaluated (as always) but are otherwise ignored.
13632 The format shall be a multibyte character sequence, beginning and ending in its initial
13633 shift state. The format is composed of zero or more directives: one or more white-space
13634 characters, an ordinary multibyte character (neither % nor a white-space character), or a
13635 conversion specification. Each conversion specification is introduced by the character %.
13636 After the %, the following appear in sequence:
13637 <ul>
13638 <li> An optional assignment-suppressing character *.
13639 <li> An optional decimal integer greater than zero that specifies the maximum field width
13640 (in characters).
13641 <!--page 295 -->
13642 <li> An optional length modifier that specifies the size of the receiving object.
13643 <li> A conversion specifier character that specifies the type of conversion to be applied.
13644 </ul>
13646 The fscanf function executes each directive of the format in turn. If a directive fails, as
13647 detailed below, the function returns. Failures are described as input failures (due to the
13648 occurrence of an encoding error or the unavailability of input characters), or matching
13649 failures (due to inappropriate input).
13651 A directive composed of white-space character(s) is executed by reading input up to the
13652 first non-white-space character (which remains unread), or until no more characters can
13653 be read.
13655 A directive that is an ordinary multibyte character is executed by reading the next
13656 characters of the stream. If any of those characters differ from the ones composing the
13657 directive, the directive fails and the differing and subsequent characters remain unread.
13658 Similarly, if end-of-file, an encoding error, or a read error prevents a character from being
13659 read, the directive fails.
13661 A directive that is a conversion specification defines a set of matching input sequences, as
13662 described below for each specifier. A conversion specification is executed in the
13663 following steps:
13665 Input white-space characters (as specified by the isspace function) are skipped, unless
13666 the specification includes a [, c, or n specifier.<sup><a href="#note250"><b>250)</b></a></sup>
13668 An input item is read from the stream, unless the specification includes an n specifier. An
13669 input item is defined as the longest sequence of input characters which does not exceed
13670 any specified field width and which is, or is a prefix of, a matching input sequence.<sup><a href="#note251"><b>251)</b></a></sup>
13671 The first character, if any, after the input item remains unread. If the length of the input
13672 item is zero, the execution of the directive fails; this condition is a matching failure unless
13673 end-of-file, an encoding error, or a read error prevented input from the stream, in which
13674 case it is an input failure.
13676 Except in the case of a % specifier, the input item (or, in the case of a %n directive, the
13677 count of input characters) is converted to a type appropriate to the conversion specifier. If
13678 the input item is not a matching sequence, the execution of the directive fails: this
13679 condition is a matching failure. Unless assignment suppression was indicated by a *, the
13680 result of the conversion is placed in the object pointed to by the first argument following
13681 the format argument that has not already received a conversion result. If this object
13682 does not have an appropriate type, or if the result of the conversion cannot be represented
13685 <!--page 296 -->
13686 in the object, the behavior is undefined.
13688 The length modifiers and their meanings are:
13689 hh Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
13690 <pre>
13691 to an argument with type pointer to signed char or unsigned char.</pre>
13692 h Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
13693 <pre>
13694 to an argument with type pointer to short int or unsigned short
13695 int.</pre>
13696 l (ell) Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
13697 <pre>
13698 to an argument with type pointer to long int or unsigned long
13699 int; that a following a, A, e, E, f, F, g, or G conversion specifier applies to
13700 an argument with type pointer to double; or that a following c, s, or [
13701 conversion specifier applies to an argument with type pointer to wchar_t.</pre>
13702 ll (ell-ell) Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
13703 <pre>
13704 to an argument with type pointer to long long int or unsigned
13705 long long int.</pre>
13706 j Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
13707 <pre>
13708 to an argument with type pointer to intmax_t or uintmax_t.</pre>
13709 z Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
13710 <pre>
13711 to an argument with type pointer to size_t or the corresponding signed
13712 integer type.</pre>
13713 t Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
13714 <pre>
13715 to an argument with type pointer to ptrdiff_t or the corresponding
13716 unsigned integer type.</pre>
13717 L Specifies that a following a, A, e, E, f, F, g, or G conversion specifier
13718 <pre>
13719 applies to an argument with type pointer to long double.</pre>
13720 If a length modifier appears with any conversion specifier other than as specified above,
13721 the behavior is undefined.
13723 The conversion specifiers and their meanings are:
13724 d Matches an optionally signed decimal integer, whose format is the same as
13725 <pre>
13726 expected for the subject sequence of the strtol function with the value 10
13727 for the base argument. The corresponding argument shall be a pointer to
13728 signed integer.</pre>
13729 i Matches an optionally signed integer, whose format is the same as expected
13730 <!--page 297 -->
13731 <pre>
13732 for the subject sequence of the strtol function with the value 0 for the
13733 base argument. The corresponding argument shall be a pointer to signed
13734 integer.</pre>
13735 o Matches an optionally signed octal integer, whose format is the same as
13736 <pre>
13737 expected for the subject sequence of the strtoul function with the value 8
13738 for the base argument. The corresponding argument shall be a pointer to
13739 unsigned integer.</pre>
13740 u Matches an optionally signed decimal integer, whose format is the same as
13741 <pre>
13742 expected for the subject sequence of the strtoul function with the value 10
13743 for the base argument. The corresponding argument shall be a pointer to
13744 unsigned integer.</pre>
13745 x Matches an optionally signed hexadecimal integer, whose format is the same
13746 <pre>
13747 as expected for the subject sequence of the strtoul function with the value
13748 16 for the base argument. The corresponding argument shall be a pointer to
13749 unsigned integer.</pre>
13750 a,e,f,g Matches an optionally signed floating-point number, infinity, or NaN, whose
13751 <pre>
13752 format is the same as expected for the subject sequence of the strtod
13753 function. The corresponding argument shall be a pointer to floating.</pre>
13754 c Matches a sequence of characters of exactly the number specified by the field
13755 <pre>
13756 width (1 if no field width is present in the directive).<sup><a href="#note252"><b>252)</b></a></sup>
13757 If no l length modifier is present, the corresponding argument shall be a
13758 pointer to the initial element of a character array large enough to accept the
13759 sequence. No null character is added.
13760 If an l length modifier is present, the input shall be a sequence of multibyte
13761 characters that begins in the initial shift state. Each multibyte character in the
13762 sequence is converted to a wide character as if by a call to the mbrtowc
13763 function, with the conversion state described by an mbstate_t object
13764 initialized to zero before the first multibyte character is converted. The
13765 corresponding argument shall be a pointer to the initial element of an array of
13766 wchar_t large enough to accept the resulting sequence of wide characters.
13767 No null wide character is added.</pre>
13768 s Matches a sequence of non-white-space characters.252)
13769 <pre>
13770 If no l length modifier is present, the corresponding argument shall be a
13771 pointer to the initial element of a character array large enough to accept the
13772 sequence and a terminating null character, which will be added automatically.
13773 If an l length modifier is present, the input shall be a sequence of multibyte</pre>
13776 <!--page 298 -->
13777 <pre>
13778 characters that begins in the initial shift state. Each multibyte character is
13779 converted to a wide character as if by a call to the mbrtowc function, with
13780 the conversion state described by an mbstate_t object initialized to zero
13781 before the first multibyte character is converted. The corresponding argument
13782 shall be a pointer to the initial element of an array of wchar_t large enough
13783 to accept the sequence and the terminating null wide character, which will be
13784 added automatically.</pre>
13785 [ Matches a nonempty sequence of characters from a set of expected characters
13786 <pre>
13787 (the scanset).252)
13788 If no l length modifier is present, the corresponding argument shall be a
13789 pointer to the initial element of a character array large enough to accept the
13790 sequence and a terminating null character, which will be added automatically.
13791 If an l length modifier is present, the input shall be a sequence of multibyte
13792 characters that begins in the initial shift state. Each multibyte character is
13793 converted to a wide character as if by a call to the mbrtowc function, with
13794 the conversion state described by an mbstate_t object initialized to zero
13795 before the first multibyte character is converted. The corresponding argument
13796 shall be a pointer to the initial element of an array of wchar_t large enough
13797 to accept the sequence and the terminating null wide character, which will be
13798 added automatically.
13799 The conversion specifier includes all subsequent characters in the format
13800 string, up to and including the matching right bracket (]). The characters
13801 between the brackets (the scanlist) compose the scanset, unless the character
13802 after the left bracket is a circumflex (^), in which case the scanset contains all
13803 characters that do not appear in the scanlist between the circumflex and the
13804 right bracket. If the conversion specifier begins with [] or [^], the right
13805 bracket character is in the scanlist and the next following right bracket
13806 character is the matching right bracket that ends the specification; otherwise
13807 the first following right bracket character is the one that ends the
13808 specification. If a - character is in the scanlist and is not the first, nor the
13809 second where the first character is a ^, nor the last character, the behavior is
13810 implementation-defined.</pre>
13811 p Matches an implementation-defined set of sequences, which should be the
13812 <!--page 299 -->
13813 <pre>
13814 same as the set of sequences that may be produced by the %p conversion of
13815 the fprintf function. The corresponding argument shall be a pointer to a
13816 pointer to void. The input item is converted to a pointer value in an
13817 implementation-defined manner. If the input item is a value converted earlier
13818 during the same program execution, the pointer that results shall compare
13819 equal to that value; otherwise the behavior of the %p conversion is undefined.</pre>
13820 n No input is consumed. The corresponding argument shall be a pointer to
13821 <pre>
13822 signed integer into which is to be written the number of characters read from
13823 the input stream so far by this call to the fscanf function. Execution of a
13824 %n directive does not increment the assignment count returned at the
13825 completion of execution of the fscanf function. No argument is converted,
13826 but one is consumed. If the conversion specification includes an assignment-
13827 suppressing character or a field width, the behavior is undefined.</pre>
13828 % Matches a single % character; no conversion or assignment occurs. The
13830 <pre>
13831 complete conversion specification shall be %%.</pre>
13832 If a conversion specification is invalid, the behavior is undefined.<sup><a href="#note253"><b>253)</b></a></sup>
13834 The conversion specifiers A, E, F, G, and X are also valid and behave the same as,
13835 respectively, a, e, f, g, and x.
13837 Trailing white space (including new-line characters) is left unread unless matched by a
13838 directive. The success of literal matches and suppressed assignments is not directly
13839 determinable other than via the %n directive.
13842 The fscanf function returns the value of the macro EOF if an input failure occurs
13843 before any conversion. Otherwise, the function returns the number of input items
13844 assigned, which can be fewer than provided for, or even zero, in the event of an early
13845 matching failure.
13847 EXAMPLE 1 The call:
13848 <pre>
13850 /* ... */
13851 int n, i; float x; char name[50];
13853 with the input line:
13854 <pre>
13856 will assign to n the value 3, to i the value 25, to x the value 5.432, and to name the sequence
13857 thompson\0.
13860 EXAMPLE 2 The call:
13861 <pre>
13863 /* ... */
13864 int i; float x; char name[50];
13866 with input:
13870 <!--page 300 -->
13871 <pre>
13873 will assign to i the value 56 and to x the value 789.0, will skip 0123, and will assign to name the
13877 EXAMPLE 3 To accept repeatedly from stdin a quantity, a unit of measure, and an item name:
13879 <pre>
13881 /* ... */
13883 do {
13885 fscanf(stdin,"%*[^\n]");
13887 If the stdin stream contains the following lines:
13888 <pre>
13889 2 quarts of oil
13890 -12.8degrees Celsius
13891 lots of luck
13892 10.0LBS of
13893 dirt
13895 the execution of the above example will be analogous to the following assignments:
13896 <pre>
13898 count = 3;
13903 count = 3;
13905 count = EOF;</pre>
13908 EXAMPLE 4 In:
13909 <pre>
13911 /* ... */
13912 int d1, d2, n1, n2, i;
13914 the value 123 is assigned to d1 and the value 3 to n1. Because %n can never get an input failure the value
13918 EXAMPLE 5 In these examples, multibyte characters do have a state-dependent encoding, and the
13919 members of the extended character set that consist of more than one byte each consist of exactly two bytes,
13920 the first of which is denoted here by a and the second by an uppercase letter, but are only recognized as
13921 such when in the alternate shift state. The shift sequences are denoted by (uparrow) and (downarrow), in which the first causes
13922 entry into the alternate shift state.
13924 After the call:
13925 <!--page 301 -->
13926 <pre>
13928 /* ... */
13929 char str[50];
13931 with the input line:
13932 <pre>
13933 a(uparrow) X Y(downarrow) bc</pre>
13934 str will contain (uparrow) X Y(downarrow)\0 assuming that none of the bytes of the shift sequences (or of the multibyte
13935 characters, in the more general case) appears to be a single-byte white-space character.
13937 In contrast, after the call:
13938 <pre>
13941 /* ... */
13942 wchar_t wstr[50];
13944 with the same input line, wstr will contain the two wide characters that correspond to X and Y and a
13945 terminating null wide character.
13947 However, the call:
13948 <pre>
13951 /* ... */
13952 wchar_t wstr[50];
13954 with the same input line will return zero due to a matching failure against the (downarrow) sequence in the format
13955 string.
13957 Assuming that the first byte of the multibyte character X is the same as the first byte of the multibyte
13958 character Y, after the call:
13959 <pre>
13962 /* ... */
13963 wchar_t wstr[50];
13965 with the same input line, zero will again be returned, but stdin will be left with a partially consumed
13966 multibyte character.
13968 <p><b> Forward references</b>: the strtod, strtof, and strtold functions (<a href="#7.20.1.3">7.20.1.3</a>), the
13969 strtol, strtoll, strtoul, and strtoull functions (<a href="#7.20.1.4">7.20.1.4</a>), conversion state
13971 <!--page 302 -->
13974 <p><small><a name="note250" href="#note250">250)</a> These white-space characters are not counted against a specified field width.
13975 </small>
13976 <p><small><a name="note251" href="#note251">251)</a> fscanf pushes back at most one input character onto the input stream. Therefore, some sequences
13977 that are acceptable to strtod, strtol, etc., are unacceptable to fscanf.
13978 </small>
13979 <p><small><a name="note252" href="#note252">252)</a> No special provisions are made for multibyte characters in the matching rules used by the c, s, and [
13980 conversion specifiers -- the extent of the input field is determined on a byte-by-byte basis. The
13981 resulting field is nevertheless a sequence of multibyte characters that begins in the initial shift state.
13982 </small>
13983 <p><small><a name="note253" href="#note253">253)</a> See ''future library directions'' (<a href="#7.26.9">7.26.9</a>).
13984 </small>
13989 <pre>
13991 int printf(const char * restrict format, ...);</pre>
13994 The printf function is equivalent to fprintf with the argument stdout interposed
13995 before the arguments to printf.
13998 The printf function returns the number of characters transmitted, or a negative value if
13999 an output or encoding error occurred.
14004 <pre>
14006 int scanf(const char * restrict format, ...);</pre>
14009 The scanf function is equivalent to fscanf with the argument stdin interposed
14010 before the arguments to scanf.
14013 The scanf function returns the value of the macro EOF if an input failure occurs before
14014 any conversion. Otherwise, the scanf function returns the number of input items
14015 assigned, which can be fewer than provided for, or even zero, in the event of an early
14016 matching failure.
14021 <pre>
14023 int snprintf(char * restrict s, size_t n,
14024 const char * restrict format, ...);</pre>
14027 The snprintf function is equivalent to fprintf, except that the output is written into
14028 an array (specified by argument s) rather than to a stream. If n is zero, nothing is written,
14029 and s may be a null pointer. Otherwise, output characters beyond the n-1st are
14030 discarded rather than being written to the array, and a null character is written at the end
14031 of the characters actually written into the array. If copying takes place between objects
14032 that overlap, the behavior is undefined.
14033 <!--page 303 -->
14036 The snprintf function returns the number of characters that would have been written
14037 had n been sufficiently large, not counting the terminating null character, or a negative
14038 value if an encoding error occurred. Thus, the null-terminated output has been
14039 completely written if and only if the returned value is nonnegative and less than n.
14044 <pre>
14046 int sprintf(char * restrict s,
14047 const char * restrict format, ...);</pre>
14050 The sprintf function is equivalent to fprintf, except that the output is written into
14051 an array (specified by the argument s) rather than to a stream. A null character is written
14052 at the end of the characters written; it is not counted as part of the returned value. If
14053 copying takes place between objects that overlap, the behavior is undefined.
14056 The sprintf function returns the number of characters written in the array, not
14057 counting the terminating null character, or a negative value if an encoding error occurred.
14062 <pre>
14064 int sscanf(const char * restrict s,
14065 const char * restrict format, ...);</pre>
14068 The sscanf function is equivalent to fscanf, except that input is obtained from a
14069 string (specified by the argument s) rather than from a stream. Reaching the end of the
14070 string is equivalent to encountering end-of-file for the fscanf function. If copying
14071 takes place between objects that overlap, the behavior is undefined.
14074 The sscanf function returns the value of the macro EOF if an input failure occurs
14075 before any conversion. Otherwise, the sscanf function returns the number of input
14076 items assigned, which can be fewer than provided for, or even zero, in the event of an
14077 early matching failure.
14078 <!--page 304 -->
14083 <pre>
14086 int vfprintf(FILE * restrict stream,
14087 const char * restrict format,
14088 va_list arg);</pre>
14091 The vfprintf function is equivalent to fprintf, with the variable argument list
14092 replaced by arg, which shall have been initialized by the va_start macro (and
14093 possibly subsequent va_arg calls). The vfprintf function does not invoke the
14097 The vfprintf function returns the number of characters transmitted, or a negative
14098 value if an output or encoding error occurred.
14100 EXAMPLE The following shows the use of the vfprintf function in a general error-reporting routine.
14101 <pre>
14104 void error(char *function_name, char *format, ...)
14105 {
14106 va_list args;
14107 va_start(args, format);
14108 // print out name of function causing error
14109 fprintf(stderr, "ERROR in %s: ", function_name);
14110 // print out remainder of message
14111 vfprintf(stderr, format, args);
14112 va_end(args);
14113 }</pre>
14118 <!--page 305 -->
14121 <p><small><a name="note254" href="#note254">254)</a> As the functions vfprintf, vfscanf, vprintf, vscanf, vsnprintf, vsprintf, and
14122 vsscanf invoke the va_arg macro, the value of arg after the return is indeterminate.
14123 </small>
14128 <pre>
14131 int vfscanf(FILE * restrict stream,
14132 const char * restrict format,
14133 va_list arg);</pre>
14136 The vfscanf function is equivalent to fscanf, with the variable argument list
14137 replaced by arg, which shall have been initialized by the va_start macro (and
14138 possibly subsequent va_arg calls). The vfscanf function does not invoke the
14139 va_end macro.254)
14142 The vfscanf function returns the value of the macro EOF if an input failure occurs
14143 before any conversion. Otherwise, the vfscanf function returns the number of input
14144 items assigned, which can be fewer than provided for, or even zero, in the event of an
14145 early matching failure.
14150 <pre>
14153 int vprintf(const char * restrict format,
14154 va_list arg);</pre>
14157 The vprintf function is equivalent to printf, with the variable argument list
14158 replaced by arg, which shall have been initialized by the va_start macro (and
14159 possibly subsequent va_arg calls). The vprintf function does not invoke the
14160 va_end macro.254)
14163 The vprintf function returns the number of characters transmitted, or a negative value
14164 if an output or encoding error occurred.
14165 <!--page 306 -->
14170 <pre>
14173 int vscanf(const char * restrict format,
14174 va_list arg);</pre>
14177 The vscanf function is equivalent to scanf, with the variable argument list replaced
14178 by arg, which shall have been initialized by the va_start macro (and possibly
14179 subsequent va_arg calls). The vscanf function does not invoke the va_end
14180 macro.254)
14183 The vscanf function returns the value of the macro EOF if an input failure occurs
14184 before any conversion. Otherwise, the vscanf function returns the number of input
14185 items assigned, which can be fewer than provided for, or even zero, in the event of an
14186 early matching failure.
14191 <pre>
14194 int vsnprintf(char * restrict s, size_t n,
14195 const char * restrict format,
14196 va_list arg);</pre>
14199 The vsnprintf function is equivalent to snprintf, with the variable argument list
14200 replaced by arg, which shall have been initialized by the va_start macro (and
14201 possibly subsequent va_arg calls). The vsnprintf function does not invoke the
14202 va_end macro.254) If copying takes place between objects that overlap, the behavior is
14203 undefined.
14206 The vsnprintf function returns the number of characters that would have been written
14207 had n been sufficiently large, not counting the terminating null character, or a negative
14208 value if an encoding error occurred. Thus, the null-terminated output has been
14209 completely written if and only if the returned value is nonnegative and less than n.
14210 <!--page 307 -->
14215 <pre>
14218 int vsprintf(char * restrict s,
14219 const char * restrict format,
14220 va_list arg);</pre>
14223 The vsprintf function is equivalent to sprintf, with the variable argument list
14224 replaced by arg, which shall have been initialized by the va_start macro (and
14225 possibly subsequent va_arg calls). The vsprintf function does not invoke the
14226 va_end macro.254) If copying takes place between objects that overlap, the behavior is
14227 undefined.
14230 The vsprintf function returns the number of characters written in the array, not
14231 counting the terminating null character, or a negative value if an encoding error occurred.
14236 <pre>
14239 int vsscanf(const char * restrict s,
14240 const char * restrict format,
14241 va_list arg);</pre>
14244 The vsscanf function is equivalent to sscanf, with the variable argument list
14245 replaced by arg, which shall have been initialized by the va_start macro (and
14246 possibly subsequent va_arg calls). The vsscanf function does not invoke the
14247 va_end macro.254)
14250 The vsscanf function returns the value of the macro EOF if an input failure occurs
14251 before any conversion. Otherwise, the vsscanf function returns the number of input
14252 items assigned, which can be fewer than provided for, or even zero, in the event of an
14253 early matching failure.
14254 <!--page 308 -->
14261 <pre>
14263 int fgetc(FILE *stream);</pre>
14266 If the end-of-file indicator for the input stream pointed to by stream is not set and a
14267 next character is present, the fgetc function obtains that character as an unsigned
14268 char converted to an int and advances the associated file position indicator for the
14269 stream (if defined).
14272 If the end-of-file indicator for the stream is set, or if the stream is at end-of-file, the end-
14273 of-file indicator for the stream is set and the fgetc function returns EOF. Otherwise, the
14274 fgetc function returns the next character from the input stream pointed to by stream.
14275 If a read error occurs, the error indicator for the stream is set and the fgetc function
14279 <p><small><a name="note255" href="#note255">255)</a> An end-of-file and a read error can be distinguished by use of the feof and ferror functions.
14280 </small>
14285 <pre>
14287 char *fgets(char * restrict s, int n,
14288 FILE * restrict stream);</pre>
14291 The fgets function reads at most one less than the number of characters specified by n
14292 from the stream pointed to by stream into the array pointed to by s. No additional
14293 characters are read after a new-line character (which is retained) or after end-of-file. A
14294 null character is written immediately after the last character read into the array.
14297 The fgets function returns s if successful. If end-of-file is encountered and no
14298 characters have been read into the array, the contents of the array remain unchanged and a
14299 null pointer is returned. If a read error occurs during the operation, the array contents are
14300 indeterminate and a null pointer is returned.
14305 <!--page 309 -->
14310 <pre>
14312 int fputc(int c, FILE *stream);</pre>
14315 The fputc function writes the character specified by c (converted to an unsigned
14316 char) to the output stream pointed to by stream, at the position indicated by the
14317 associated file position indicator for the stream (if defined), and advances the indicator
14318 appropriately. If the file cannot support positioning requests, or if the stream was opened
14319 with append mode, the character is appended to the output stream.
14322 The fputc function returns the character written. If a write error occurs, the error
14323 indicator for the stream is set and fputc returns EOF.
14328 <pre>
14330 int fputs(const char * restrict s,
14331 FILE * restrict stream);</pre>
14334 The fputs function writes the string pointed to by s to the stream pointed to by
14335 stream. The terminating null character is not written.
14338 The fputs function returns EOF if a write error occurs; otherwise it returns a
14339 nonnegative value.
14344 <pre>
14346 int getc(FILE *stream);</pre>
14349 The getc function is equivalent to fgetc, except that if it is implemented as a macro, it
14350 may evaluate stream more than once, so the argument should never be an expression
14351 with side effects.
14352 <!--page 310 -->
14355 The getc function returns the next character from the input stream pointed to by
14356 stream. If the stream is at end-of-file, the end-of-file indicator for the stream is set and
14357 getc returns EOF. If a read error occurs, the error indicator for the stream is set and
14358 getc returns EOF.
14363 <pre>
14365 int getchar(void);</pre>
14368 The getchar function is equivalent to getc with the argument stdin.
14371 The getchar function returns the next character from the input stream pointed to by
14372 stdin. If the stream is at end-of-file, the end-of-file indicator for the stream is set and
14373 getchar returns EOF. If a read error occurs, the error indicator for the stream is set and
14374 getchar returns EOF.
14379 <pre>
14381 char *gets(char *s);</pre>
14384 The gets function reads characters from the input stream pointed to by stdin, into the
14385 array pointed to by s, until end-of-file is encountered or a new-line character is read.
14386 Any new-line character is discarded, and a null character is written immediately after the
14387 last character read into the array.
14390 The gets function returns s if successful. If end-of-file is encountered and no
14391 characters have been read into the array, the contents of the array remain unchanged and a
14392 null pointer is returned. If a read error occurs during the operation, the array contents are
14393 indeterminate and a null pointer is returned.
14395 <!--page 311 -->
14400 <pre>
14402 int putc(int c, FILE *stream);</pre>
14405 The putc function is equivalent to fputc, except that if it is implemented as a macro, it
14406 may evaluate stream more than once, so that argument should never be an expression
14407 with side effects.
14410 The putc function returns the character written. If a write error occurs, the error
14411 indicator for the stream is set and putc returns EOF.
14416 <pre>
14418 int putchar(int c);</pre>
14421 The putchar function is equivalent to putc with the second argument stdout.
14424 The putchar function returns the character written. If a write error occurs, the error
14425 indicator for the stream is set and putchar returns EOF.
14430 <pre>
14432 int puts(const char *s);</pre>
14435 The puts function writes the string pointed to by s to the stream pointed to by stdout,
14436 and appends a new-line character to the output. The terminating null character is not
14437 written.
14440 The puts function returns EOF if a write error occurs; otherwise it returns a nonnegative
14441 value.
14442 <!--page 312 -->
14447 <pre>
14449 int ungetc(int c, FILE *stream);</pre>
14452 The ungetc function pushes the character specified by c (converted to an unsigned
14453 char) back onto the input stream pointed to by stream. Pushed-back characters will be
14454 returned by subsequent reads on that stream in the reverse order of their pushing. A
14455 successful intervening call (with the stream pointed to by stream) to a file positioning
14456 function (fseek, fsetpos, or rewind) discards any pushed-back characters for the
14457 stream. The external storage corresponding to the stream is unchanged.
14459 One character of pushback is guaranteed. If the ungetc function is called too many
14460 times on the same stream without an intervening read or file positioning operation on that
14461 stream, the operation may fail.
14463 If the value of c equals that of the macro EOF, the operation fails and the input stream is
14464 unchanged.
14466 A successful call to the ungetc function clears the end-of-file indicator for the stream.
14467 The value of the file position indicator for the stream after reading or discarding all
14468 pushed-back characters shall be the same as it was before the characters were pushed
14469 back. For a text stream, the value of its file position indicator after a successful call to the
14470 ungetc function is unspecified until all pushed-back characters are read or discarded.
14471 For a binary stream, its file position indicator is decremented by each successful call to
14472 the ungetc function; if its value was zero before a call, it is indeterminate after the
14476 The ungetc function returns the character pushed back after conversion, or EOF if the
14477 operation fails.
14483 <!--page 313 -->
14486 <p><small><a name="note256" href="#note256">256)</a> See ''future library directions'' (<a href="#7.26.9">7.26.9</a>).
14487 </small>
14494 <pre>
14496 size_t fread(void * restrict ptr,
14497 size_t size, size_t nmemb,
14498 FILE * restrict stream);</pre>
14501 The fread function reads, into the array pointed to by ptr, up to nmemb elements
14502 whose size is specified by size, from the stream pointed to by stream. For each
14503 object, size calls are made to the fgetc function and the results stored, in the order
14504 read, in an array of unsigned char exactly overlaying the object. The file position
14505 indicator for the stream (if defined) is advanced by the number of characters successfully
14506 read. If an error occurs, the resulting value of the file position indicator for the stream is
14507 indeterminate. If a partial element is read, its value is indeterminate.
14510 The fread function returns the number of elements successfully read, which may be
14511 less than nmemb if a read error or end-of-file is encountered. If size or nmemb is zero,
14512 fread returns zero and the contents of the array and the state of the stream remain
14513 unchanged.
14518 <pre>
14520 size_t fwrite(const void * restrict ptr,
14521 size_t size, size_t nmemb,
14522 FILE * restrict stream);</pre>
14525 The fwrite function writes, from the array pointed to by ptr, up to nmemb elements
14526 whose size is specified by size, to the stream pointed to by stream. For each object,
14527 size calls are made to the fputc function, taking the values (in order) from an array of
14528 unsigned char exactly overlaying the object. The file position indicator for the
14529 stream (if defined) is advanced by the number of characters successfully written. If an
14530 error occurs, the resulting value of the file position indicator for the stream is
14531 indeterminate.
14532 <!--page 314 -->
14535 The fwrite function returns the number of elements successfully written, which will be
14536 less than nmemb only if a write error is encountered. If size or nmemb is zero,
14537 fwrite returns zero and the state of the stream remains unchanged.
14544 <pre>
14546 int fgetpos(FILE * restrict stream,
14547 fpos_t * restrict pos);</pre>
14550 The fgetpos function stores the current values of the parse state (if any) and file
14551 position indicator for the stream pointed to by stream in the object pointed to by pos.
14552 The values stored contain unspecified information usable by the fsetpos function for
14553 repositioning the stream to its position at the time of the call to the fgetpos function.
14556 If successful, the fgetpos function returns zero; on failure, the fgetpos function
14557 returns nonzero and stores an implementation-defined positive value in errno.
14563 <pre>
14565 int fseek(FILE *stream, long int offset, int whence);</pre>
14568 The fseek function sets the file position indicator for the stream pointed to by stream.
14569 If a read or write error occurs, the error indicator for the stream is set and fseek fails.
14571 For a binary stream, the new position, measured in characters from the beginning of the
14572 file, is obtained by adding offset to the position specified by whence. The specified
14573 position is the beginning of the file if whence is SEEK_SET, the current value of the file
14574 position indicator if SEEK_CUR, or end-of-file if SEEK_END. A binary stream need not
14575 meaningfully support fseek calls with a whence value of SEEK_END.
14577 For a text stream, either offset shall be zero, or offset shall be a value returned by
14578 an earlier successful call to the ftell function on a stream associated with the same file
14579 and whence shall be SEEK_SET.
14580 <!--page 315 -->
14582 After determining the new position, a successful call to the fseek function undoes any
14583 effects of the ungetc function on the stream, clears the end-of-file indicator for the
14584 stream, and then establishes the new position. After a successful fseek call, the next
14585 operation on an update stream may be either input or output.
14588 The fseek function returns nonzero only for a request that cannot be satisfied.
14594 <pre>
14596 int fsetpos(FILE *stream, const fpos_t *pos);</pre>
14599 The fsetpos function sets the mbstate_t object (if any) and file position indicator
14600 for the stream pointed to by stream according to the value of the object pointed to by
14601 pos, which shall be a value obtained from an earlier successful call to the fgetpos
14602 function on a stream associated with the same file. If a read or write error occurs, the
14603 error indicator for the stream is set and fsetpos fails.
14605 A successful call to the fsetpos function undoes any effects of the ungetc function
14606 on the stream, clears the end-of-file indicator for the stream, and then establishes the new
14607 parse state and position. After a successful fsetpos call, the next operation on an
14608 update stream may be either input or output.
14611 If successful, the fsetpos function returns zero; on failure, the fsetpos function
14612 returns nonzero and stores an implementation-defined positive value in errno.
14617 <pre>
14619 long int ftell(FILE *stream);</pre>
14622 The ftell function obtains the current value of the file position indicator for the stream
14623 pointed to by stream. For a binary stream, the value is the number of characters from
14624 the beginning of the file. For a text stream, its file position indicator contains unspecified
14625 information, usable by the fseek function for returning the file position indicator for the
14626 stream to its position at the time of the ftell call; the difference between two such
14627 return values is not necessarily a meaningful measure of the number of characters written
14628 <!--page 316 -->
14629 or read.
14632 If successful, the ftell function returns the current value of the file position indicator
14633 for the stream. On failure, the ftell function returns -1L and stores an
14634 implementation-defined positive value in errno.
14639 <pre>
14641 void rewind(FILE *stream);</pre>
14644 The rewind function sets the file position indicator for the stream pointed to by
14645 stream to the beginning of the file. It is equivalent to
14646 <pre>
14648 except that the error indicator for the stream is also cleared.
14651 The rewind function returns no value.
14658 <pre>
14660 void clearerr(FILE *stream);</pre>
14663 The clearerr function clears the end-of-file and error indicators for the stream pointed
14664 to by stream.
14667 The clearerr function returns no value.
14668 <!--page 317 -->
14673 <pre>
14675 int feof(FILE *stream);</pre>
14678 The feof function tests the end-of-file indicator for the stream pointed to by stream.
14681 The feof function returns nonzero if and only if the end-of-file indicator is set for
14682 stream.
14687 <pre>
14689 int ferror(FILE *stream);</pre>
14692 The ferror function tests the error indicator for the stream pointed to by stream.
14695 The ferror function returns nonzero if and only if the error indicator is set for
14696 stream.
14701 <pre>
14703 void perror(const char *s);</pre>
14706 The perror function maps the error number in the integer expression errno to an
14707 error message. It writes a sequence of characters to the standard error stream thus: first
14708 (if s is not a null pointer and the character pointed to by s is not the null character), the
14709 string pointed to by s followed by a colon (:) and a space; then an appropriate error
14710 message string followed by a new-line character. The contents of the error message
14711 strings are the same as those returned by the strerror function with argument errno.
14714 The perror function returns no value.
14716 <!--page 318 -->
14720 The header <a href="#7.20"><stdlib.h></a> declares five types and several functions of general utility, and
14724 <pre>
14725 div_t</pre>
14726 which is a structure type that is the type of the value returned by the div function,
14727 <pre>
14728 ldiv_t</pre>
14729 which is a structure type that is the type of the value returned by the ldiv function, and
14730 <pre>
14731 lldiv_t</pre>
14732 which is a structure type that is the type of the value returned by the lldiv function.
14735 <pre>
14736 EXIT_FAILURE</pre>
14737 and
14738 <pre>
14739 EXIT_SUCCESS</pre>
14740 which expand to integer constant expressions that can be used as the argument to the
14741 exit function to return unsuccessful or successful termination status, respectively, to the
14742 host environment;
14743 <pre>
14744 RAND_MAX</pre>
14745 which expands to an integer constant expression that is the maximum value returned by
14746 the rand function; and
14747 <pre>
14748 MB_CUR_MAX</pre>
14749 which expands to a positive integer expression with type size_t that is the maximum
14750 number of bytes in a multibyte character for the extended character set specified by the
14751 current locale (category LC_CTYPE), which is never greater than MB_LEN_MAX.
14756 <!--page 319 -->
14759 <p><small><a name="note257" href="#note257">257)</a> See ''future library directions'' (<a href="#7.26.10">7.26.10</a>).
14760 </small>
14764 The functions atof, atoi, atol, and atoll need not affect the value of the integer
14765 expression errno on an error. If the value of the result cannot be represented, the
14766 behavior is undefined.
14771 <pre>
14773 double atof(const char *nptr);</pre>
14776 The atof function converts the initial portion of the string pointed to by nptr to
14777 double representation. Except for the behavior on error, it is equivalent to
14778 <pre>
14779 strtod(nptr, (char **)NULL)</pre>
14782 The atof function returns the converted value.
14783 <p><b> Forward references</b>: the strtod, strtof, and strtold functions (<a href="#7.20.1.3">7.20.1.3</a>).
14788 <pre>
14790 int atoi(const char *nptr);
14791 long int atol(const char *nptr);
14792 long long int atoll(const char *nptr);</pre>
14795 The atoi, atol, and atoll functions convert the initial portion of the string pointed
14796 to by nptr to int, long int, and long long int representation, respectively.
14797 Except for the behavior on error, they are equivalent to
14798 <pre>
14799 atoi: (int)strtol(nptr, (char **)NULL, 10)
14800 atol: strtol(nptr, (char **)NULL, 10)
14804 The atoi, atol, and atoll functions return the converted value.
14807 <!--page 320 -->
14809 <h5><a name="7.20.1.3" href="#7.20.1.3">7.20.1.3 The strtod, strtof, and strtold functions</a></h5>
14812 <pre>
14814 double strtod(const char * restrict nptr,
14815 char ** restrict endptr);
14816 float strtof(const char * restrict nptr,
14817 char ** restrict endptr);
14818 long double strtold(const char * restrict nptr,
14819 char ** restrict endptr);</pre>
14822 The strtod, strtof, and strtold functions convert the initial portion of the string
14823 pointed to by nptr to double, float, and long double representation,
14824 respectively. First, they decompose the input string into three parts: an initial, possibly
14825 empty, sequence of white-space characters (as specified by the isspace function), a
14826 subject sequence resembling a floating-point constant or representing an infinity or NaN;
14827 and a final string of one or more unrecognized characters, including the terminating null
14828 character of the input string. Then, they attempt to convert the subject sequence to a
14829 floating-point number, and return the result.
14831 The expected form of the subject sequence is an optional plus or minus sign, then one of
14832 the following:
14833 <ul>
14834 <li> a nonempty sequence of decimal digits optionally containing a decimal-point
14837 decimal-point character, then an optional binary exponent part as defined in <a href="#6.4.4.2">6.4.4.2</a>;
14838 <li> INF or INFINITY, ignoring case
14839 <li> NAN or NAN(n-char-sequenceopt), ignoring case in the NAN part, where:
14840 <pre>
14841 n-char-sequence:
14842 digit
14843 nondigit
14844 n-char-sequence digit
14845 n-char-sequence nondigit</pre>
14846 </ul>
14847 The subject sequence is defined as the longest initial subsequence of the input string,
14848 starting with the first non-white-space character, that is of the expected form. The subject
14849 sequence contains no characters if the input string is not of the expected form.
14851 If the subject sequence has the expected form for a floating-point number, the sequence of
14852 characters starting with the first digit or the decimal-point character (whichever occurs
14853 first) is interpreted as a floating constant according to the rules of <a href="#6.4.4.2">6.4.4.2</a>, except that the
14854 <!--page 321 -->
14855 decimal-point character is used in place of a period, and that if neither an exponent part
14856 nor a decimal-point character appears in a decimal floating point number, or if a binary
14857 exponent part does not appear in a hexadecimal floating point number, an exponent part
14858 of the appropriate type with value zero is assumed to follow the last digit in the string. If
14859 the subject sequence begins with a minus sign, the sequence is interpreted as negated.<sup><a href="#note258"><b>258)</b></a></sup>
14860 A character sequence INF or INFINITY is interpreted as an infinity, if representable in
14861 the return type, else like a floating constant that is too large for the range of the return
14862 type. A character sequence NAN or NAN(n-char-sequenceopt), is interpreted as a quiet
14863 NaN, if supported in the return type, else like a subject sequence part that does not have
14864 the expected form; the meaning of the n-char sequences is implementation-defined.<sup><a href="#note259"><b>259)</b></a></sup> A
14865 pointer to the final string is stored in the object pointed to by endptr, provided that
14866 endptr is not a null pointer.
14868 If the subject sequence has the hexadecimal form and FLT_RADIX is a power of 2, the
14869 value resulting from the conversion is correctly rounded.
14871 In other than the "C" locale, additional locale-specific subject sequence forms may be
14872 accepted.
14874 If the subject sequence is empty or does not have the expected form, no conversion is
14875 performed; the value of nptr is stored in the object pointed to by endptr, provided
14876 that endptr is not a null pointer.
14877 Recommended practice
14879 If the subject sequence has the hexadecimal form, FLT_RADIX is not a power of 2, and
14880 the result is not exactly representable, the result should be one of the two numbers in the
14881 appropriate internal format that are adjacent to the hexadecimal floating source value,
14882 with the extra stipulation that the error should have a correct sign for the current rounding
14883 direction.
14885 If the subject sequence has the decimal form and at most DECIMAL_DIG (defined in
14886 <a href="#7.7"><float.h></a>) significant digits, the result should be correctly rounded. If the subject
14887 sequence D has the decimal form and more than DECIMAL_DIG significant digits,
14888 consider the two bounding, adjacent decimal strings L and U, both having
14889 DECIMAL_DIG significant digits, such that the values of L, D, and U satisfy L <= D <= U.
14890 The result should be one of the (equal or adjacent) values that would be obtained by
14891 correctly rounding L and U according to the current rounding direction, with the extra
14893 <!--page 322 -->
14894 stipulation that the error with respect to D should have a correct sign for the current
14898 The functions return the converted value, if any. If no conversion could be performed,
14899 zero is returned. If the correct value is outside the range of representable values, plus or
14900 minus HUGE_VAL, HUGE_VALF, or HUGE_VALL is returned (according to the return
14901 type and sign of the value), and the value of the macro ERANGE is stored in errno. If
14902 the result underflows (<a href="#7.12.1">7.12.1</a>), the functions return a value whose magnitude is no greater
14903 than the smallest normalized positive number in the return type; whether errno acquires
14904 the value ERANGE is implementation-defined.
14907 <p><small><a name="note258" href="#note258">258)</a> It is unspecified whether a minus-signed sequence is converted to a negative number directly or by
14908 negating the value resulting from converting the corresponding unsigned sequence (see <a href="#F.5">F.5</a>); the two
14909 methods may yield different results if rounding is toward positive or negative infinity. In either case,
14910 the functions honor the sign of zero if floating-point arithmetic supports signed zeros.
14911 </small>
14912 <p><small><a name="note259" href="#note259">259)</a> An implementation may use the n-char sequence to determine extra information to be represented in
14913 the NaN's significand.
14914 </small>
14915 <p><small><a name="note260" href="#note260">260)</a> DECIMAL_DIG, defined in <a href="#7.7"><float.h></a>, should be sufficiently large that L and U will usually round
14916 to the same internal floating value, but if not will round to adjacent values.
14917 </small>
14919 <h5><a name="7.20.1.4" href="#7.20.1.4">7.20.1.4 The strtol, strtoll, strtoul, and strtoull functions</a></h5>
14922 <pre>
14924 long int strtol(
14925 const char * restrict nptr,
14926 char ** restrict endptr,
14927 int base);
14928 long long int strtoll(
14929 const char * restrict nptr,
14930 char ** restrict endptr,
14931 int base);
14932 unsigned long int strtoul(
14933 const char * restrict nptr,
14934 char ** restrict endptr,
14935 int base);
14936 unsigned long long int strtoull(
14937 const char * restrict nptr,
14938 char ** restrict endptr,
14939 int base);</pre>
14942 The strtol, strtoll, strtoul, and strtoull functions convert the initial
14943 portion of the string pointed to by nptr to long int, long long int, unsigned
14944 long int, and unsigned long long int representation, respectively. First,
14945 they decompose the input string into three parts: an initial, possibly empty, sequence of
14946 white-space characters (as specified by the isspace function), a subject sequence
14949 <!--page 323 -->
14950 resembling an integer represented in some radix determined by the value of base, and a
14951 final string of one or more unrecognized characters, including the terminating null
14952 character of the input string. Then, they attempt to convert the subject sequence to an
14953 integer, and return the result.
14955 If the value of base is zero, the expected form of the subject sequence is that of an
14956 integer constant as described in <a href="#6.4.4.1">6.4.4.1</a>, optionally preceded by a plus or minus sign, but
14958 expected form of the subject sequence is a sequence of letters and digits representing an
14959 integer with the radix specified by base, optionally preceded by a plus or minus sign,
14960 but not including an integer suffix. The letters from a (or A) through z (or Z) are
14963 optionally precede the sequence of letters and digits, following the sign if present.
14965 The subject sequence is defined as the longest initial subsequence of the input string,
14966 starting with the first non-white-space character, that is of the expected form. The subject
14967 sequence contains no characters if the input string is empty or consists entirely of white
14968 space, or if the first non-white-space character is other than a sign or a permissible letter
14969 or digit.
14971 If the subject sequence has the expected form and the value of base is zero, the sequence
14972 of characters starting with the first digit is interpreted as an integer constant according to
14973 the rules of <a href="#6.4.4.1">6.4.4.1</a>. If the subject sequence has the expected form and the value of base
14974 is between 2 and 36, it is used as the base for conversion, ascribing to each letter its value
14975 as given above. If the subject sequence begins with a minus sign, the value resulting from
14976 the conversion is negated (in the return type). A pointer to the final string is stored in the
14977 object pointed to by endptr, provided that endptr is not a null pointer.
14979 In other than the "C" locale, additional locale-specific subject sequence forms may be
14980 accepted.
14982 If the subject sequence is empty or does not have the expected form, no conversion is
14983 performed; the value of nptr is stored in the object pointed to by endptr, provided
14984 that endptr is not a null pointer.
14987 The strtol, strtoll, strtoul, and strtoull functions return the converted
14988 value, if any. If no conversion could be performed, zero is returned. If the correct value
14989 is outside the range of representable values, LONG_MIN, LONG_MAX, LLONG_MIN,
14990 LLONG_MAX, ULONG_MAX, or ULLONG_MAX is returned (according to the return type
14991 and sign of the value, if any), and the value of the macro ERANGE is stored in errno.
14992 <!--page 324 -->
14994 <h4><a name="7.20.2" href="#7.20.2">7.20.2 Pseudo-random sequence generation functions</a></h4>
14999 <pre>
15001 int rand(void);</pre>
15004 The rand function computes a sequence of pseudo-random integers in the range 0 to
15005 RAND_MAX.
15007 The implementation shall behave as if no library function calls the rand function.
15010 The rand function returns a pseudo-random integer.
15011 Environmental limits
15013 The value of the RAND_MAX macro shall be at least 32767.
15018 <pre>
15020 void srand(unsigned int seed);</pre>
15023 The srand function uses the argument as a seed for a new sequence of pseudo-random
15024 numbers to be returned by subsequent calls to rand. If srand is then called with the
15025 same seed value, the sequence of pseudo-random numbers shall be repeated. If rand is
15026 called before any calls to srand have been made, the same sequence shall be generated
15027 as when srand is first called with a seed value of 1.
15029 The implementation shall behave as if no library function calls the srand function.
15032 The srand function returns no value.
15034 EXAMPLE The following functions define a portable implementation of rand and srand.
15035 <!--page 325 -->
15036 <pre>
15037 static unsigned long int next = 1;
15038 int rand(void) // RAND_MAX assumed to be 32767
15039 {
15042 }
15043 void srand(unsigned int seed)
15044 {
15045 next = seed;
15046 }</pre>
15051 The order and contiguity of storage allocated by successive calls to the calloc,
15052 malloc, and realloc functions is unspecified. The pointer returned if the allocation
15053 succeeds is suitably aligned so that it may be assigned to a pointer to any type of object
15054 and then used to access such an object or an array of such objects in the space allocated
15055 (until the space is explicitly deallocated). The lifetime of an allocated object extends
15056 from the allocation until the deallocation. Each such allocation shall yield a pointer to an
15057 object disjoint from any other object. The pointer returned points to the start (lowest byte
15058 address) of the allocated space. If the space cannot be allocated, a null pointer is
15059 returned. If the size of the space requested is zero, the behavior is implementation-
15060 defined: either a null pointer is returned, or the behavior is as if the size were some
15061 nonzero value, except that the returned pointer shall not be used to access an object.
15066 <pre>
15068 void *calloc(size_t nmemb, size_t size);</pre>
15071 The calloc function allocates space for an array of nmemb objects, each of whose size
15072 is size. The space is initialized to all bits zero.<sup><a href="#note261"><b>261)</b></a></sup>
15075 The calloc function returns either a null pointer or a pointer to the allocated space.
15078 <p><small><a name="note261" href="#note261">261)</a> Note that this need not be the same as the representation of floating-point zero or a null pointer
15079 constant.
15080 </small>
15085 <pre>
15087 void free(void *ptr);</pre>
15090 The free function causes the space pointed to by ptr to be deallocated, that is, made
15091 available for further allocation. If ptr is a null pointer, no action occurs. Otherwise, if
15092 the argument does not match a pointer earlier returned by the calloc, malloc, or
15095 <!--page 326 -->
15096 realloc function, or if the space has been deallocated by a call to free or realloc,
15097 the behavior is undefined.
15100 The free function returns no value.
15105 <pre>
15107 void *malloc(size_t size);</pre>
15110 The malloc function allocates space for an object whose size is specified by size and
15111 whose value is indeterminate.
15114 The malloc function returns either a null pointer or a pointer to the allocated space.
15119 <pre>
15121 void *realloc(void *ptr, size_t size);</pre>
15124 The realloc function deallocates the old object pointed to by ptr and returns a
15125 pointer to a new object that has the size specified by size. The contents of the new
15126 object shall be the same as that of the old object prior to deallocation, up to the lesser of
15127 the new and old sizes. Any bytes in the new object beyond the size of the old object have
15128 indeterminate values.
15130 If ptr is a null pointer, the realloc function behaves like the malloc function for the
15131 specified size. Otherwise, if ptr does not match a pointer earlier returned by the
15132 calloc, malloc, or realloc function, or if the space has been deallocated by a call
15133 to the free or realloc function, the behavior is undefined. If memory for the new
15134 object cannot be allocated, the old object is not deallocated and its value is unchanged.
15137 The realloc function returns a pointer to the new object (which may have the same
15138 value as a pointer to the old object), or a null pointer if the new object could not be
15139 allocated.
15140 <!--page 327 -->
15147 <pre>
15149 void abort(void);</pre>
15152 The abort function causes abnormal program termination to occur, unless the signal
15153 SIGABRT is being caught and the signal handler does not return. Whether open streams
15154 with unwritten buffered data are flushed, open streams are closed, or temporary files are
15155 removed is implementation-defined. An implementation-defined form of the status
15156 unsuccessful termination is returned to the host environment by means of the function
15157 call raise(SIGABRT).
15160 The abort function does not return to its caller.
15165 <pre>
15167 int atexit(void (*func)(void));</pre>
15170 The atexit function registers the function pointed to by func, to be called without
15171 arguments at normal program termination.
15172 Environmental limits
15174 The implementation shall support the registration of at least 32 functions.
15177 The atexit function returns zero if the registration succeeds, nonzero if it fails.
15183 <pre>
15185 void exit(int status);</pre>
15188 The exit function causes normal program termination to occur. If more than one call to
15189 the exit function is executed by a program, the behavior is undefined.
15190 <!--page 328 -->
15192 First, all functions registered by the atexit function are called, in the reverse order of
15193 their registration,<sup><a href="#note262"><b>262)</b></a></sup> except that a function is called after any previously registered
15194 functions that had already been called at the time it was registered. If, during the call to
15195 any such function, a call to the longjmp function is made that would terminate the call
15196 to the registered function, the behavior is undefined.
15198 Next, all open streams with unwritten buffered data are flushed, all open streams are
15199 closed, and all files created by the tmpfile function are removed.
15201 Finally, control is returned to the host environment. If the value of status is zero or
15202 EXIT_SUCCESS, an implementation-defined form of the status successful termination is
15203 returned. If the value of status is EXIT_FAILURE, an implementation-defined form
15204 of the status unsuccessful termination is returned. Otherwise the status returned is
15205 implementation-defined.
15208 The exit function cannot return to its caller.
15211 <p><small><a name="note262" href="#note262">262)</a> Each function is called as many times as it was registered, and in the correct order with respect to
15212 other registered functions.
15213 </small>
15218 <pre>
15220 void _Exit(int status);</pre>
15223 The _Exit function causes normal program termination to occur and control to be
15224 returned to the host environment. No functions registered by the atexit function or
15225 signal handlers registered by the signal function are called. The status returned to the
15226 host environment is determined in the same way as for the exit function (<a href="#7.20.4.3">7.20.4.3</a>).
15227 Whether open streams with unwritten buffered data are flushed, open streams are closed,
15228 or temporary files are removed is implementation-defined.
15231 The _Exit function cannot return to its caller.
15236 <!--page 329 -->
15241 <pre>
15243 char *getenv(const char *name);</pre>
15246 The getenv function searches an environment list, provided by the host environment,
15247 for a string that matches the string pointed to by name. The set of environment names
15248 and the method for altering the environment list are implementation-defined.
15250 The implementation shall behave as if no library function calls the getenv function.
15253 The getenv function returns a pointer to a string associated with the matched list
15254 member. The string pointed to shall not be modified by the program, but may be
15255 overwritten by a subsequent call to the getenv function. If the specified name cannot
15256 be found, a null pointer is returned.
15261 <pre>
15263 int system(const char *string);</pre>
15266 If string is a null pointer, the system function determines whether the host
15267 environment has a command processor. If string is not a null pointer, the system
15268 function passes the string pointed to by string to that command processor to be
15269 executed in a manner which the implementation shall document; this might then cause the
15270 program calling system to behave in a non-conforming manner or to terminate.
15273 If the argument is a null pointer, the system function returns nonzero only if a
15274 command processor is available. If the argument is not a null pointer, and the system
15275 function does return, it returns an implementation-defined value.
15276 <!--page 330 -->
15280 These utilities make use of a comparison function to search or sort arrays of unspecified
15281 type. Where an argument declared as size_t nmemb specifies the length of the array
15282 for a function, nmemb can have the value zero on a call to that function; the comparison
15283 function is not called, a search finds no matching element, and sorting performs no
15284 rearrangement. Pointer arguments on such a call shall still have valid values, as described
15287 The implementation shall ensure that the second argument of the comparison function
15288 (when called from bsearch), or both arguments (when called from qsort), are
15289 pointers to elements of the array.<sup><a href="#note263"><b>263)</b></a></sup> The first argument when called from bsearch
15290 shall equal key.
15292 The comparison function shall not alter the contents of the array. The implementation
15293 may reorder elements of the array between calls to the comparison function, but shall not
15294 alter the contents of any individual element.
15296 When the same objects (consisting of size bytes, irrespective of their current positions
15297 in the array) are passed more than once to the comparison function, the results shall be
15298 consistent with one another. That is, for qsort they shall define a total ordering on the
15299 array, and for bsearch the same object shall always compare the same way with the
15300 key.
15302 A sequence point occurs immediately before and immediately after each call to the
15303 comparison function, and also between any call to the comparison function and any
15304 movement of the objects passed as arguments to that call.
15307 <p><small><a name="note263" href="#note263">263)</a> That is, if the value passed is p, then the following expressions are always nonzero:
15309 <pre>
15310 ((char *)p - (char *)base) % size == 0
15311 (char *)p >= (char *)base
15313 </small>
15318 <pre>
15320 void *bsearch(const void *key, const void *base,
15321 size_t nmemb, size_t size,
15322 int (*compar)(const void *, const void *));</pre>
15325 The bsearch function searches an array of nmemb objects, the initial element of which
15326 is pointed to by base, for an element that matches the object pointed to by key. The
15329 <!--page 331 -->
15330 size of each element of the array is specified by size.
15332 The comparison function pointed to by compar is called with two arguments that point
15333 to the key object and to an array element, in that order. The function shall return an
15334 integer less than, equal to, or greater than zero if the key object is considered,
15335 respectively, to be less than, to match, or to be greater than the array element. The array
15336 shall consist of: all the elements that compare less than, all the elements that compare
15337 equal to, and all the elements that compare greater than the key object, in that order.<sup><a href="#note264"><b>264)</b></a></sup>
15340 The bsearch function returns a pointer to a matching element of the array, or a null
15341 pointer if no match is found. If two elements compare as equal, which element is
15342 matched is unspecified.
15345 <p><small><a name="note264" href="#note264">264)</a> In practice, the entire array is sorted according to the comparison function.
15346 </small>
15351 <pre>
15353 void qsort(void *base, size_t nmemb, size_t size,
15354 int (*compar)(const void *, const void *));</pre>
15357 The qsort function sorts an array of nmemb objects, the initial element of which is
15358 pointed to by base. The size of each object is specified by size.
15360 The contents of the array are sorted into ascending order according to a comparison
15361 function pointed to by compar, which is called with two arguments that point to the
15362 objects being compared. The function shall return an integer less than, equal to, or
15363 greater than zero if the first argument is considered to be respectively less than, equal to,
15364 or greater than the second.
15366 If two elements compare as equal, their order in the resulting sorted array is unspecified.
15369 The qsort function returns no value.
15374 <!--page 332 -->
15381 <pre>
15383 int abs(int j);
15384 long int labs(long int j);
15385 long long int llabs(long long int j);</pre>
15388 The abs, labs, and llabs functions compute the absolute value of an integer j. If the
15389 result cannot be represented, the behavior is undefined.<sup><a href="#note265"><b>265)</b></a></sup>
15392 The abs, labs, and llabs, functions return the absolute value.
15395 <p><small><a name="note265" href="#note265">265)</a> The absolute value of the most negative number cannot be represented in two's complement.
15396 </small>
15401 <pre>
15403 div_t div(int numer, int denom);
15404 ldiv_t ldiv(long int numer, long int denom);
15405 lldiv_t lldiv(long long int numer, long long int denom);</pre>
15408 The div, ldiv, and lldiv, functions compute numer / denom and numer %
15409 denom in a single operation.
15412 The div, ldiv, and lldiv functions return a structure of type div_t, ldiv_t, and
15413 lldiv_t, respectively, comprising both the quotient and the remainder. The structures
15414 shall contain (in either order) the members quot (the quotient) and rem (the remainder),
15415 each of which has the same type as the arguments numer and denom. If either part of
15416 the result cannot be represented, the behavior is undefined.
15421 <!--page 333 -->
15423 <h4><a name="7.20.7" href="#7.20.7">7.20.7 Multibyte/wide character conversion functions</a></h4>
15425 The behavior of the multibyte character functions is affected by the LC_CTYPE category
15426 of the current locale. For a state-dependent encoding, each function is placed into its
15427 initial conversion state by a call for which its character pointer argument, s, is a null
15428 pointer. Subsequent calls with s as other than a null pointer cause the internal conversion
15429 state of the function to be altered as necessary. A call with s as a null pointer causes
15430 these functions to return a nonzero value if encodings have state dependency, and zero
15431 otherwise.<sup><a href="#note266"><b>266)</b></a></sup> Changing the LC_CTYPE category causes the conversion state of these
15432 functions to be indeterminate.
15435 <p><small><a name="note266" href="#note266">266)</a> If the locale employs special bytes to change the shift state, these bytes do not produce separate wide
15436 character codes, but are grouped with an adjacent multibyte character.
15437 </small>
15442 <pre>
15444 int mblen(const char *s, size_t n);</pre>
15447 If s is not a null pointer, the mblen function determines the number of bytes contained
15448 in the multibyte character pointed to by s. Except that the conversion state of the
15449 mbtowc function is not affected, it is equivalent to
15451 <pre>
15453 The implementation shall behave as if no library function calls the mblen function.
15456 If s is a null pointer, the mblen function returns a nonzero or zero value, if multibyte
15457 character encodings, respectively, do or do not have state-dependent encodings. If s is
15458 not a null pointer, the mblen function either returns 0 (if s points to the null character),
15459 or returns the number of bytes that are contained in the multibyte character (if the next n
15460 or fewer bytes form a valid multibyte character), or returns -1 (if they do not form a valid
15461 multibyte character).
15467 <!--page 334 -->
15472 <pre>
15474 int mbtowc(wchar_t * restrict pwc,
15475 const char * restrict s,
15476 size_t n);</pre>
15479 If s is not a null pointer, the mbtowc function inspects at most n bytes beginning with
15480 the byte pointed to by s to determine the number of bytes needed to complete the next
15481 multibyte character (including any shift sequences). If the function determines that the
15482 next multibyte character is complete and valid, it determines the value of the
15483 corresponding wide character and then, if pwc is not a null pointer, stores that value in
15484 the object pointed to by pwc. If the corresponding wide character is the null wide
15485 character, the function is left in the initial conversion state.
15487 The implementation shall behave as if no library function calls the mbtowc function.
15490 If s is a null pointer, the mbtowc function returns a nonzero or zero value, if multibyte
15491 character encodings, respectively, do or do not have state-dependent encodings. If s is
15492 not a null pointer, the mbtowc function either returns 0 (if s points to the null character),
15493 or returns the number of bytes that are contained in the converted multibyte character (if
15494 the next n or fewer bytes form a valid multibyte character), or returns -1 (if they do not
15495 form a valid multibyte character).
15497 In no case will the value returned be greater than n or the value of the MB_CUR_MAX
15498 macro.
15503 <pre>
15505 int wctomb(char *s, wchar_t wc);</pre>
15508 The wctomb function determines the number of bytes needed to represent the multibyte
15509 character corresponding to the wide character given by wc (including any shift
15510 sequences), and stores the multibyte character representation in the array whose first
15511 element is pointed to by s (if s is not a null pointer). At most MB_CUR_MAX characters
15512 are stored. If wc is a null wide character, a null byte is stored, preceded by any shift
15513 sequence needed to restore the initial shift state, and the function is left in the initial
15514 conversion state.
15515 <!--page 335 -->
15517 The implementation shall behave as if no library function calls the wctomb function.
15520 If s is a null pointer, the wctomb function returns a nonzero or zero value, if multibyte
15521 character encodings, respectively, do or do not have state-dependent encodings. If s is
15522 not a null pointer, the wctomb function returns -1 if the value of wc does not correspond
15523 to a valid multibyte character, or returns the number of bytes that are contained in the
15524 multibyte character corresponding to the value of wc.
15526 In no case will the value returned be greater than the value of the MB_CUR_MAX macro.
15528 <h4><a name="7.20.8" href="#7.20.8">7.20.8 Multibyte/wide string conversion functions</a></h4>
15530 The behavior of the multibyte string functions is affected by the LC_CTYPE category of
15531 the current locale.
15536 <pre>
15538 size_t mbstowcs(wchar_t * restrict pwcs,
15539 const char * restrict s,
15540 size_t n);</pre>
15543 The mbstowcs function converts a sequence of multibyte characters that begins in the
15544 initial shift state from the array pointed to by s into a sequence of corresponding wide
15545 characters and stores not more than n wide characters into the array pointed to by pwcs.
15546 No multibyte characters that follow a null character (which is converted into a null wide
15547 character) will be examined or converted. Each multibyte character is converted as if by
15548 a call to the mbtowc function, except that the conversion state of the mbtowc function is
15549 not affected.
15551 No more than n elements will be modified in the array pointed to by pwcs. If copying
15552 takes place between objects that overlap, the behavior is undefined.
15555 If an invalid multibyte character is encountered, the mbstowcs function returns
15556 (size_t)(-1). Otherwise, the mbstowcs function returns the number of array
15557 elements modified, not including a terminating null wide character, if any.<sup><a href="#note267"><b>267)</b></a></sup>
15562 <!--page 336 -->
15565 <p><small><a name="note267" href="#note267">267)</a> The array will not be null-terminated if the value returned is n.
15566 </small>
15571 <pre>
15573 size_t wcstombs(char * restrict s,
15574 const wchar_t * restrict pwcs,
15575 size_t n);</pre>
15578 The wcstombs function converts a sequence of wide characters from the array pointed
15579 to by pwcs into a sequence of corresponding multibyte characters that begins in the
15580 initial shift state, and stores these multibyte characters into the array pointed to by s,
15581 stopping if a multibyte character would exceed the limit of n total bytes or if a null
15582 character is stored. Each wide character is converted as if by a call to the wctomb
15583 function, except that the conversion state of the wctomb function is not affected.
15585 No more than n bytes will be modified in the array pointed to by s. If copying takes place
15586 between objects that overlap, the behavior is undefined.
15589 If a wide character is encountered that does not correspond to a valid multibyte character,
15590 the wcstombs function returns (size_t)(-1). Otherwise, the wcstombs function
15591 returns the number of bytes modified, not including a terminating null character, if
15592 any.267)
15593 <!--page 337 -->
15599 The header <a href="#7.21"><string.h></a> declares one type and several functions, and defines one
15600 macro useful for manipulating arrays of character type and other objects treated as arrays
15601 of character type.<sup><a href="#note268"><b>268)</b></a></sup> The type is size_t and the macro is NULL (both described in
15602 <a href="#7.17">7.17</a>). Various methods are used for determining the lengths of the arrays, but in all cases
15603 a char * or void * argument points to the initial (lowest addressed) character of the
15604 array. If an array is accessed beyond the end of an object, the behavior is undefined.
15606 Where an argument declared as size_t n specifies the length of the array for a
15607 function, n can have the value zero on a call to that function. Unless explicitly stated
15608 otherwise in the description of a particular function in this subclause, pointer arguments
15609 on such a call shall still have valid values, as described in <a href="#7.1.4">7.1.4</a>. On such a call, a
15610 function that locates a character finds no occurrence, a function that compares two
15611 character sequences returns zero, and a function that copies characters copies zero
15612 characters.
15614 For all functions in this subclause, each character shall be interpreted as if it had the type
15615 unsigned char (and therefore every possible object representation is valid and has a
15616 different value).
15619 <p><small><a name="note268" href="#note268">268)</a> See ''future library directions'' (<a href="#7.26.11">7.26.11</a>).
15620 </small>
15627 <pre>
15629 void *memcpy(void * restrict s1,
15630 const void * restrict s2,
15631 size_t n);</pre>
15634 The memcpy function copies n characters from the object pointed to by s2 into the
15635 object pointed to by s1. If copying takes place between objects that overlap, the behavior
15636 is undefined.
15639 The memcpy function returns the value of s1.
15644 <!--page 338 -->
15649 <pre>
15651 void *memmove(void *s1, const void *s2, size_t n);</pre>
15654 The memmove function copies n characters from the object pointed to by s2 into the
15655 object pointed to by s1. Copying takes place as if the n characters from the object
15656 pointed to by s2 are first copied into a temporary array of n characters that does not
15657 overlap the objects pointed to by s1 and s2, and then the n characters from the
15658 temporary array are copied into the object pointed to by s1.
15661 The memmove function returns the value of s1.
15666 <pre>
15668 char *strcpy(char * restrict s1,
15669 const char * restrict s2);</pre>
15672 The strcpy function copies the string pointed to by s2 (including the terminating null
15673 character) into the array pointed to by s1. If copying takes place between objects that
15674 overlap, the behavior is undefined.
15677 The strcpy function returns the value of s1.
15682 <pre>
15684 char *strncpy(char * restrict s1,
15685 const char * restrict s2,
15686 size_t n);</pre>
15689 The strncpy function copies not more than n characters (characters that follow a null
15690 character are not copied) from the array pointed to by s2 to the array pointed to by
15691 <!--page 339 -->
15692 s1.<sup><a href="#note269"><b>269)</b></a></sup> If copying takes place between objects that overlap, the behavior is undefined.
15694 If the array pointed to by s2 is a string that is shorter than n characters, null characters
15695 are appended to the copy in the array pointed to by s1, until n characters in all have been
15696 written.
15699 The strncpy function returns the value of s1.
15702 <p><small><a name="note269" href="#note269">269)</a> Thus, if there is no null character in the first n characters of the array pointed to by s2, the result will
15703 not be null-terminated.
15704 </small>
15711 <pre>
15713 char *strcat(char * restrict s1,
15714 const char * restrict s2);</pre>
15717 The strcat function appends a copy of the string pointed to by s2 (including the
15718 terminating null character) to the end of the string pointed to by s1. The initial character
15719 of s2 overwrites the null character at the end of s1. If copying takes place between
15720 objects that overlap, the behavior is undefined.
15723 The strcat function returns the value of s1.
15728 <pre>
15730 char *strncat(char * restrict s1,
15731 const char * restrict s2,
15732 size_t n);</pre>
15735 The strncat function appends not more than n characters (a null character and
15736 characters that follow it are not appended) from the array pointed to by s2 to the end of
15737 the string pointed to by s1. The initial character of s2 overwrites the null character at the
15738 end of s1. A terminating null character is always appended to the result.<sup><a href="#note270"><b>270)</b></a></sup> If copying
15740 <!--page 340 -->
15741 takes place between objects that overlap, the behavior is undefined.
15744 The strncat function returns the value of s1.
15748 <p><small><a name="note270" href="#note270">270)</a> Thus, the maximum number of characters that can end up in the array pointed to by s1 is
15749 strlen(s1)+n+1.
15750 </small>
15754 The sign of a nonzero value returned by the comparison functions memcmp, strcmp,
15755 and strncmp is determined by the sign of the difference between the values of the first
15756 pair of characters (both interpreted as unsigned char) that differ in the objects being
15757 compared.
15762 <pre>
15764 int memcmp(const void *s1, const void *s2, size_t n);</pre>
15767 The memcmp function compares the first n characters of the object pointed to by s1 to
15768 the first n characters of the object pointed to by s2.<sup><a href="#note271"><b>271)</b></a></sup>
15771 The memcmp function returns an integer greater than, equal to, or less than zero,
15772 accordingly as the object pointed to by s1 is greater than, equal to, or less than the object
15773 pointed to by s2.
15776 <p><small><a name="note271" href="#note271">271)</a> The contents of ''holes'' used as padding for purposes of alignment within structure objects are
15777 indeterminate. Strings shorter than their allocated space and unions may also cause problems in
15778 comparison.
15779 </small>
15784 <pre>
15786 int strcmp(const char *s1, const char *s2);</pre>
15789 The strcmp function compares the string pointed to by s1 to the string pointed to by
15790 s2.
15793 The strcmp function returns an integer greater than, equal to, or less than zero,
15794 accordingly as the string pointed to by s1 is greater than, equal to, or less than the string
15796 <!--page 341 -->
15797 pointed to by s2.
15802 <pre>
15804 int strcoll(const char *s1, const char *s2);</pre>
15807 The strcoll function compares the string pointed to by s1 to the string pointed to by
15808 s2, both interpreted as appropriate to the LC_COLLATE category of the current locale.
15811 The strcoll function returns an integer greater than, equal to, or less than zero,
15812 accordingly as the string pointed to by s1 is greater than, equal to, or less than the string
15813 pointed to by s2 when both are interpreted as appropriate to the current locale.
15818 <pre>
15820 int strncmp(const char *s1, const char *s2, size_t n);</pre>
15823 The strncmp function compares not more than n characters (characters that follow a
15824 null character are not compared) from the array pointed to by s1 to the array pointed to
15825 by s2.
15828 The strncmp function returns an integer greater than, equal to, or less than zero,
15829 accordingly as the possibly null-terminated array pointed to by s1 is greater than, equal
15830 to, or less than the possibly null-terminated array pointed to by s2.
15835 <pre>
15837 size_t strxfrm(char * restrict s1,
15838 const char * restrict s2,
15839 size_t n);</pre>
15842 The strxfrm function transforms the string pointed to by s2 and places the resulting
15843 string into the array pointed to by s1. The transformation is such that if the strcmp
15844 function is applied to two transformed strings, it returns a value greater than, equal to, or
15845 <!--page 342 -->
15846 less than zero, corresponding to the result of the strcoll function applied to the same
15847 two original strings. No more than n characters are placed into the resulting array
15848 pointed to by s1, including the terminating null character. If n is zero, s1 is permitted to
15849 be a null pointer. If copying takes place between objects that overlap, the behavior is
15850 undefined.
15853 The strxfrm function returns the length of the transformed string (not including the
15854 terminating null character). If the value returned is n or more, the contents of the array
15855 pointed to by s1 are indeterminate.
15857 EXAMPLE The value of the following expression is the size of the array needed to hold the
15858 transformation of the string pointed to by s.
15859 <pre>
15868 <pre>
15870 void *memchr(const void *s, int c, size_t n);</pre>
15873 The memchr function locates the first occurrence of c (converted to an unsigned
15874 char) in the initial n characters (each interpreted as unsigned char) of the object
15875 pointed to by s.
15878 The memchr function returns a pointer to the located character, or a null pointer if the
15879 character does not occur in the object.
15884 <pre>
15886 char *strchr(const char *s, int c);</pre>
15889 The strchr function locates the first occurrence of c (converted to a char) in the
15890 string pointed to by s. The terminating null character is considered to be part of the
15891 string.
15894 The strchr function returns a pointer to the located character, or a null pointer if the
15895 character does not occur in the string.
15896 <!--page 343 -->
15901 <pre>
15903 size_t strcspn(const char *s1, const char *s2);</pre>
15906 The strcspn function computes the length of the maximum initial segment of the string
15907 pointed to by s1 which consists entirely of characters not from the string pointed to by
15908 s2.
15911 The strcspn function returns the length of the segment.
15916 <pre>
15918 char *strpbrk(const char *s1, const char *s2);</pre>
15921 The strpbrk function locates the first occurrence in the string pointed to by s1 of any
15922 character from the string pointed to by s2.
15925 The strpbrk function returns a pointer to the character, or a null pointer if no character
15926 from s2 occurs in s1.
15931 <pre>
15933 char *strrchr(const char *s, int c);</pre>
15936 The strrchr function locates the last occurrence of c (converted to a char) in the
15937 string pointed to by s. The terminating null character is considered to be part of the
15938 string.
15941 The strrchr function returns a pointer to the character, or a null pointer if c does not
15942 occur in the string.
15943 <!--page 344 -->
15948 <pre>
15950 size_t strspn(const char *s1, const char *s2);</pre>
15953 The strspn function computes the length of the maximum initial segment of the string
15954 pointed to by s1 which consists entirely of characters from the string pointed to by s2.
15957 The strspn function returns the length of the segment.
15962 <pre>
15964 char *strstr(const char *s1, const char *s2);</pre>
15967 The strstr function locates the first occurrence in the string pointed to by s1 of the
15968 sequence of characters (excluding the terminating null character) in the string pointed to
15969 by s2.
15972 The strstr function returns a pointer to the located string, or a null pointer if the string
15973 is not found. If s2 points to a string with zero length, the function returns s1.
15978 <pre>
15980 char *strtok(char * restrict s1,
15981 const char * restrict s2);</pre>
15984 A sequence of calls to the strtok function breaks the string pointed to by s1 into a
15985 sequence of tokens, each of which is delimited by a character from the string pointed to
15986 by s2. The first call in the sequence has a non-null first argument; subsequent calls in the
15987 sequence have a null first argument. The separator string pointed to by s2 may be
15988 different from call to call.
15990 The first call in the sequence searches the string pointed to by s1 for the first character
15991 that is not contained in the current separator string pointed to by s2. If no such character
15992 is found, then there are no tokens in the string pointed to by s1 and the strtok function
15993 <!--page 345 -->
15994 returns a null pointer. If such a character is found, it is the start of the first token.
15996 The strtok function then searches from there for a character that is contained in the
15997 current separator string. If no such character is found, the current token extends to the
15998 end of the string pointed to by s1, and subsequent searches for a token will return a null
15999 pointer. If such a character is found, it is overwritten by a null character, which
16000 terminates the current token. The strtok function saves a pointer to the following
16001 character, from which the next search for a token will start.
16003 Each subsequent call, with a null pointer as the value of the first argument, starts
16004 searching from the saved pointer and behaves as described above.
16006 The implementation shall behave as if no library function calls the strtok function.
16009 The strtok function returns a pointer to the first character of a token, or a null pointer
16010 if there is no token.
16012 EXAMPLE
16013 <pre>
16015 static char str[] = "?a???b,,,#c";
16016 char *t;
16028 <pre>
16030 void *memset(void *s, int c, size_t n);</pre>
16033 The memset function copies the value of c (converted to an unsigned char) into
16034 each of the first n characters of the object pointed to by s.
16037 The memset function returns the value of s.
16038 <!--page 346 -->
16043 <pre>
16045 char *strerror(int errnum);</pre>
16048 The strerror function maps the number in errnum to a message string. Typically,
16049 the values for errnum come from errno, but strerror shall map any value of type
16050 int to a message.
16052 The implementation shall behave as if no library function calls the strerror function.
16055 The strerror function returns a pointer to the string, the contents of which are locale-
16056 specific. The array pointed to shall not be modified by the program, but may be
16057 overwritten by a subsequent call to the strerror function.
16062 <pre>
16064 size_t strlen(const char *s);</pre>
16067 The strlen function computes the length of the string pointed to by s.
16070 The strlen function returns the number of characters that precede the terminating null
16071 character.
16072 <!--page 347 -->
16076 The header <a href="#7.22"><tgmath.h></a> includes the headers <a href="#7.12"><math.h></a> and <a href="#7.3"><complex.h></a> and
16077 defines several type-generic macros.
16079 Of the <a href="#7.12"><math.h></a> and <a href="#7.3"><complex.h></a> functions without an f (float) or l (long
16080 double) suffix, several have one or more parameters whose corresponding real type is
16081 double. For each such function, except modf, there is a corresponding type-generic
16082 macro.<sup><a href="#note272"><b>272)</b></a></sup> The parameters whose corresponding real type is double in the function
16083 synopsis are generic parameters. Use of the macro invokes a function whose
16084 corresponding real type and type domain are determined by the arguments for the generic
16087 Use of the macro invokes a function whose generic parameters have the corresponding
16088 real type determined as follows:
16089 <ul>
16090 <li> First, if any argument for generic parameters has type long double, the type
16091 determined is long double.
16092 <li> Otherwise, if any argument for generic parameters has type double or is of integer
16093 type, the type determined is double.
16094 <li> Otherwise, the type determined is float.
16095 </ul>
16097 For each unsuffixed function in <a href="#7.12"><math.h></a> for which there is a function in
16098 <a href="#7.3"><complex.h></a> with the same name except for a c prefix, the corresponding type-
16099 generic macro (for both functions) has the same name as the function in <a href="#7.12"><math.h></a>. The
16100 corresponding type-generic macro for fabs and cabs is fabs.
16105 <!--page 348 -->
16106 <pre>
16108 function function macro
16109 acos cacos acos
16110 asin casin asin
16111 atan catan atan
16112 acosh cacosh acosh
16113 asinh casinh asinh
16114 atanh catanh atanh
16115 cos ccos cos
16116 sin csin sin
16117 tan ctan tan
16118 cosh ccosh cosh
16119 sinh csinh sinh
16120 tanh ctanh tanh
16121 exp cexp exp
16122 log clog log
16123 pow cpow pow
16124 sqrt csqrt sqrt
16125 fabs cabs fabs</pre>
16126 If at least one argument for a generic parameter is complex, then use of the macro invokes
16127 a complex function; otherwise, use of the macro invokes a real function.
16129 For each unsuffixed function in <a href="#7.12"><math.h></a> without a c-prefixed counterpart in
16130 <a href="#7.3"><complex.h></a> (except modf), the corresponding type-generic macro has the same
16131 name as the function. These type-generic macros are:
16132 <pre>
16133 atan2 fma llround remainder
16134 cbrt fmax log10 remquo
16135 ceil fmin log1p rint
16136 copysign fmod log2 round
16137 erf frexp logb scalbn
16138 erfc hypot lrint scalbln
16139 exp2 ilogb lround tgamma
16140 expm1 ldexp nearbyint trunc
16141 fdim lgamma nextafter
16142 floor llrint nexttoward</pre>
16143 If all arguments for generic parameters are real, then use of the macro invokes a real
16144 function; otherwise, use of the macro results in undefined behavior.
16146 For each unsuffixed function in <a href="#7.3"><complex.h></a> that is not a c-prefixed counterpart to a
16147 function in <a href="#7.12"><math.h></a>, the corresponding type-generic macro has the same name as the
16148 function. These type-generic macros are:
16149 <!--page 349 -->
16150 <pre>
16151 carg conj creal
16152 cimag cproj</pre>
16153 Use of the macro with any real or complex argument invokes a complex function.
16155 EXAMPLE With the declarations
16156 <pre>
16158 int n;
16159 float f;
16160 double d;
16161 long double ld;
16162 float complex fc;
16163 double complex dc;
16164 long double complex ldc;</pre>
16165 functions invoked by use of type-generic macros are shown in the following table:
16166 <!--page 350 -->
16167 <pre>
16168 macro use invokes
16169 exp(n) exp(n), the function
16170 acosh(f) acoshf(f)
16171 sin(d) sin(d), the function
16172 atan(ld) atanl(ld)
16173 log(fc) clogf(fc)
16174 sqrt(dc) csqrt(dc)
16175 pow(ldc, f) cpowl(ldc, f)
16176 remainder(n, n) remainder(n, n), the function
16177 nextafter(d, f) nextafter(d, f), the function
16178 nexttoward(f, ld) nexttowardf(f, ld)
16179 copysign(n, ld) copysignl(n, ld)
16180 ceil(fc) undefined behavior
16181 rint(dc) undefined behavior
16182 fmax(ldc, ld) undefined behavior
16183 carg(n) carg(n), the function
16184 cproj(f) cprojf(f)
16185 creal(d) creal(d), the function
16186 cimag(ld) cimagl(ld)
16187 fabs(fc) cabsf(fc)
16188 carg(dc) carg(dc), the function
16189 cproj(ldc) cprojl(ldc)</pre>
16192 <p><small><a name="note272" href="#note272">272)</a> Like other function-like macros in Standard libraries, each type-generic macro can be suppressed to
16193 make available the corresponding ordinary function.
16194 </small>
16195 <p><small><a name="note273" href="#note273">273)</a> If the type of the argument is not compatible with the type of the parameter for the selected function,
16196 the behavior is undefined.
16197 </small>
16203 The header <a href="#7.23"><time.h></a> defines two macros, and declares several types and functions for
16204 manipulating time. Many functions deal with a calendar time that represents the current
16205 date (according to the Gregorian calendar) and time. Some functions deal with local
16206 time, which is the calendar time expressed for some specific time zone, and with Daylight
16207 Saving Time, which is a temporary change in the algorithm for determining local time.
16208 The local time zone and Daylight Saving Time are implementation-defined.
16211 <pre>
16212 CLOCKS_PER_SEC</pre>
16213 which expands to an expression with type clock_t (described below) that is the
16214 number per second of the value returned by the clock function.
16217 <pre>
16218 clock_t</pre>
16219 and
16220 <pre>
16221 time_t</pre>
16222 which are arithmetic types capable of representing times; and
16223 <pre>
16224 struct tm</pre>
16225 which holds the components of a calendar time, called the broken-down time.
16227 The range and precision of times representable in clock_t and time_t are
16228 implementation-defined. The tm structure shall contain at least the following members,
16229 in any order. The semantics of the members and their normal ranges are expressed in the
16231 <pre>
16237 int tm_year; // years since 1900
16240 int tm_isdst; // Daylight Saving Time flag</pre>
16244 <!--page 351 -->
16245 The value of tm_isdst is positive if Daylight Saving Time is in effect, zero if Daylight
16246 Saving Time is not in effect, and negative if the information is not available.
16249 <p><small><a name="note274" href="#note274">274)</a> The range [0, 60] for tm_sec allows for a positive leap second.
16250 </small>
16257 <pre>
16259 clock_t clock(void);</pre>
16262 The clock function determines the processor time used.
16265 The clock function returns the implementation's best approximation to the processor
16266 time used by the program since the beginning of an implementation-defined era related
16267 only to the program invocation. To determine the time in seconds, the value returned by
16268 the clock function should be divided by the value of the macro CLOCKS_PER_SEC. If
16269 the processor time used is not available or its value cannot be represented, the function
16273 <p><small><a name="note275" href="#note275">275)</a> In order to measure the time spent in a program, the clock function should be called at the start of
16274 the program and its return value subtracted from the value returned by subsequent calls.
16275 </small>
16280 <pre>
16282 double difftime(time_t time1, time_t time0);</pre>
16285 The difftime function computes the difference between two calendar times: time1 -
16286 time0.
16289 The difftime function returns the difference expressed in seconds as a double.
16294 <!--page 352 -->
16299 <pre>
16301 time_t mktime(struct tm *timeptr);</pre>
16304 The mktime function converts the broken-down time, expressed as local time, in the
16305 structure pointed to by timeptr into a calendar time value with the same encoding as
16306 that of the values returned by the time function. The original values of the tm_wday
16307 and tm_yday components of the structure are ignored, and the original values of the
16308 other components are not restricted to the ranges indicated above.<sup><a href="#note276"><b>276)</b></a></sup> On successful
16309 completion, the values of the tm_wday and tm_yday components of the structure are
16310 set appropriately, and the other components are set to represent the specified calendar
16311 time, but with their values forced to the ranges indicated above; the final value of
16312 tm_mday is not set until tm_mon and tm_year are determined.
16315 The mktime function returns the specified calendar time encoded as a value of type
16316 time_t. If the calendar time cannot be represented, the function returns the value
16317 (time_t)(-1).
16320 <pre>
16323 static const char *const wday[] = {
16326 };
16327 struct tm time_str;
16328 /* ... */</pre>
16333 <!--page 353 -->
16334 <pre>
16337 time_str.tm_mday = 4;
16338 time_str.tm_hour = 0;
16339 time_str.tm_min = 0;
16340 time_str.tm_sec = 1;
16341 time_str.tm_isdst = -1;
16343 time_str.tm_wday = 7;
16348 <p><small><a name="note276" href="#note276">276)</a> Thus, a positive or zero value for tm_isdst causes the mktime function to presume initially that
16349 Daylight Saving Time, respectively, is or is not in effect for the specified time. A negative value
16350 causes it to attempt to determine whether Daylight Saving Time is in effect for the specified time.
16351 </small>
16356 <pre>
16358 time_t time(time_t *timer);</pre>
16361 The time function determines the current calendar time. The encoding of the value is
16362 unspecified.
16365 The time function returns the implementation's best approximation to the current
16366 calendar time. The value (time_t)(-1) is returned if the calendar time is not
16367 available. If timer is not a null pointer, the return value is also assigned to the object it
16368 points to.
16372 Except for the strftime function, these functions each return a pointer to one of two
16373 types of static objects: a broken-down time structure or an array of char. Execution of
16374 any of the functions that return a pointer to one of these object types may overwrite the
16375 information in any object of the same type pointed to by the value returned from any
16376 previous call to any of them. The implementation shall behave as if no other library
16377 functions call these functions.
16382 <pre>
16384 char *asctime(const struct tm *timeptr);</pre>
16387 The asctime function converts the broken-down time in the structure pointed to by
16388 timeptr into a string in the form
16389 <!--page 354 -->
16390 <pre>
16392 using the equivalent of the following algorithm.
16393 char *asctime(const struct tm *timeptr)
16394 {
16395 <pre>
16398 };
16402 };
16403 static char result[26];
16404 sprintf(result, "%.3s %.3s%3d %.2d:%.2d:%.2d %d\n",
16405 wday_name[timeptr->tm_wday],
16406 mon_name[timeptr->tm_mon],
16410 return result;</pre>
16411 }
16414 The asctime function returns a pointer to the string.
16419 <pre>
16421 char *ctime(const time_t *timer);</pre>
16424 The ctime function converts the calendar time pointed to by timer to local time in the
16425 form of a string. It is equivalent to
16426 <pre>
16427 asctime(localtime(timer))</pre>
16430 The ctime function returns the pointer returned by the asctime function with that
16431 broken-down time as argument.
16433 <!--page 355 -->
16438 <pre>
16440 struct tm *gmtime(const time_t *timer);</pre>
16443 The gmtime function converts the calendar time pointed to by timer into a broken-
16444 down time, expressed as UTC.
16447 The gmtime function returns a pointer to the broken-down time, or a null pointer if the
16448 specified time cannot be converted to UTC.
16453 <pre>
16455 struct tm *localtime(const time_t *timer);</pre>
16458 The localtime function converts the calendar time pointed to by timer into a
16459 broken-down time, expressed as local time.
16462 The localtime function returns a pointer to the broken-down time, or a null pointer if
16463 the specified time cannot be converted to local time.
16468 <pre>
16470 size_t strftime(char * restrict s,
16471 size_t maxsize,
16472 const char * restrict format,
16473 const struct tm * restrict timeptr);</pre>
16476 The strftime function places characters into the array pointed to by s as controlled by
16477 the string pointed to by format. The format shall be a multibyte character sequence,
16478 beginning and ending in its initial shift state. The format string consists of zero or
16479 more conversion specifiers and ordinary multibyte characters. A conversion specifier
16480 consists of a % character, possibly followed by an E or O modifier character (described
16481 below), followed by a character that determines the behavior of the conversion specifier.
16482 All ordinary multibyte characters (including the terminating null character) are copied
16483 <!--page 356 -->
16484 unchanged into the array. If copying takes place between objects that overlap, the
16485 behavior is undefined. No more than maxsize characters are placed into the array.
16487 Each conversion specifier is replaced by appropriate characters as described in the
16488 following list. The appropriate characters are determined using the LC_TIME category
16489 of the current locale and by the values of zero or more members of the broken-down time
16490 structure pointed to by timeptr, as specified in brackets in the description. If any of
16491 the specified values is outside the normal range, the characters stored are unspecified.
16492 %a is replaced by the locale's abbreviated weekday name. [tm_wday]
16493 %A is replaced by the locale's full weekday name. [tm_wday]
16494 %b is replaced by the locale's abbreviated month name. [tm_mon]
16495 %B is replaced by the locale's full month name. [tm_mon]
16496 %c is replaced by the locale's appropriate date and time representation. [all specified
16497 <pre>
16499 %C is replaced by the year divided by 100 and truncated to an integer, as a decimal
16500 <pre>
16503 %D is equivalent to ''%m/%d/%y''. [tm_mon, tm_mday, tm_year]
16505 <pre>
16506 preceded by a space. [tm_mday]</pre>
16507 %F is equivalent to ''%Y-%m-%d'' (the ISO 8601 date format). [tm_year, tm_mon,
16508 <pre>
16509 tm_mday]</pre>
16510 %g is replaced by the last 2 digits of the week-based year (see below) as a decimal
16511 <pre>
16513 %G is replaced by the week-based year (see below) as a decimal number (e.g., 1997).
16514 <pre>
16515 [tm_year, tm_wday, tm_yday]</pre>
16516 %h is equivalent to ''%b''. [tm_mon]
16522 %n is replaced by a new-line character.
16523 %p is replaced by the locale's equivalent of the AM/PM designations associated with a
16524 <pre>
16526 %r is replaced by the locale's 12-hour clock time. [tm_hour, tm_min, tm_sec]
16527 %R is equivalent to ''%H:%M''. [tm_hour, tm_min]
16529 %t is replaced by a horizontal-tab character.
16530 %T is equivalent to ''%H:%M:%S'' (the ISO 8601 time format). [tm_hour, tm_min,
16531 <!--page 357 -->
16532 <pre>
16533 tm_sec]</pre>
16535 <pre>
16537 %U is replaced by the week number of the year (the first Sunday as the first day of week
16538 <pre>
16540 %V is replaced by the ISO 8601 week number (see below) as a decimal number
16541 <pre>
16544 <pre>
16545 [tm_wday]</pre>
16546 %W is replaced by the week number of the year (the first Monday as the first day of
16547 <pre>
16549 %x is replaced by the locale's appropriate date representation. [all specified in <a href="#7.23.1">7.23.1</a>]
16550 %X is replaced by the locale's appropriate time representation. [all specified in <a href="#7.23.1">7.23.1</a>]
16552 <pre>
16553 [tm_year]</pre>
16554 %Y is replaced by the year as a decimal number (e.g., 1997). [tm_year]
16556 <pre>
16557 hours 30 minutes behind UTC, west of Greenwich), or by no characters if no time
16558 zone is determinable. [tm_isdst]</pre>
16559 %Z is replaced by the locale's time zone name or abbreviation, or by no characters if no
16560 <pre>
16561 time zone is determinable. [tm_isdst]</pre>
16562 %% is replaced by %.
16564 Some conversion specifiers can be modified by the inclusion of an E or O modifier
16565 character to indicate an alternative format or specification. If the alternative format or
16566 specification does not exist for the current locale, the modifier is ignored.
16567 %Ec is replaced by the locale's alternative date and time representation.
16568 %EC is replaced by the name of the base year (period) in the locale's alternative
16569 <pre>
16570 representation.</pre>
16571 %Ex is replaced by the locale's alternative date representation.
16572 %EX is replaced by the locale's alternative time representation.
16573 %Ey is replaced by the offset from %EC (year only) in the locale's alternative
16574 <pre>
16575 representation.</pre>
16576 %EY is replaced by the locale's full alternative year representation.
16577 %Od is replaced by the day of the month, using the locale's alternative numeric symbols
16578 <pre>
16579 (filled as needed with leading zeros, or with leading spaces if there is no alternative
16580 symbol for zero).</pre>
16581 %Oe is replaced by the day of the month, using the locale's alternative numeric symbols
16582 <pre>
16583 (filled as needed with leading spaces).</pre>
16584 %OH is replaced by the hour (24-hour clock), using the locale's alternative numeric
16585 <!--page 358 -->
16586 <pre>
16587 symbols.</pre>
16588 %OI is replaced by the hour (12-hour clock), using the locale's alternative numeric
16589 <pre>
16590 symbols.</pre>
16591 %Om is replaced by the month, using the locale's alternative numeric symbols.
16592 %OM is replaced by the minutes, using the locale's alternative numeric symbols.
16593 %OS is replaced by the seconds, using the locale's alternative numeric symbols.
16594 %Ou is replaced by the ISO 8601 weekday as a number in the locale's alternative
16595 <pre>
16597 %OU is replaced by the week number, using the locale's alternative numeric symbols.
16598 %OV is replaced by the ISO 8601 week number, using the locale's alternative numeric
16599 <pre>
16600 symbols.</pre>
16601 %Ow is replaced by the weekday as a number, using the locale's alternative numeric
16602 <pre>
16603 symbols.</pre>
16604 %OW is replaced by the week number of the year, using the locale's alternative numeric
16605 <pre>
16606 symbols.</pre>
16607 %Oy is replaced by the last 2 digits of the year, using the locale's alternative numeric
16609 <pre>
16610 symbols.</pre>
16611 %g, %G, and %V give values according to the ISO 8601 week-based year. In this system,
16613 which is also the week that includes the first Thursday of the year, and is also the first
16614 week that contains at least four days in the year. If the first Monday of January is the
16619 %V is replaced by 01.
16621 If a conversion specifier is not one of the above, the behavior is undefined.
16623 In the "C" locale, the E and O modifiers are ignored and the replacement strings for the
16624 following specifiers are:
16625 %a the first three characters of %A.
16626 %A one of ''Sunday'', ''Monday'', ... , ''Saturday''.
16627 %b the first three characters of %B.
16628 %B one of ''January'', ''February'', ... , ''December''.
16629 %c equivalent to ''%a %b %e %T %Y''.
16630 %p one of ''AM'' or ''PM''.
16631 %r equivalent to ''%I:%M:%S %p''.
16632 %x equivalent to ''%m/%d/%y''.
16633 %X equivalent to %T.
16634 %Z implementation-defined.
16635 <!--page 359 -->
16638 If the total number of resulting characters including the terminating null character is not
16639 more than maxsize, the strftime function returns the number of characters placed
16640 into the array pointed to by s not including the terminating null character. Otherwise,
16641 zero is returned and the contents of the array are indeterminate.
16642 <!--page 360 -->
16644 <h3><a name="7.24" href="#7.24">7.24 Extended multibyte and wide character utilities <wchar.h></a></h3>
16648 The header <a href="#7.24"><wchar.h></a> declares four data types, one tag, four macros, and many
16652 <pre>
16653 mbstate_t</pre>
16654 which is an object type other than an array type that can hold the conversion state
16655 information necessary to convert between sequences of multibyte characters and wide
16656 characters;
16657 <pre>
16658 wint_t</pre>
16659 which is an integer type unchanged by default argument promotions that can hold any
16660 value corresponding to members of the extended character set, as well as at least one
16661 value that does not correspond to any member of the extended character set (see WEOF
16663 <pre>
16664 struct tm</pre>
16665 which is declared as an incomplete structure type (the contents are described in <a href="#7.23.1">7.23.1</a>).
16669 <pre>
16670 WEOF</pre>
16671 which expands to a constant expression of type wint_t whose value does not
16672 correspond to any member of the extended character set.<sup><a href="#note279"><b>279)</b></a></sup> It is accepted (and returned)
16673 by several functions in this subclause to indicate end-of-file, that is, no more input from a
16674 stream. It is also used as a wide character value that does not correspond to any member
16675 of the extended character set.
16677 The functions declared are grouped as follows:
16678 <ul>
16679 <li> Functions that perform input and output of wide characters, or multibyte characters,
16680 or both;
16681 <li> Functions that provide wide string numeric conversion;
16682 <li> Functions that perform general wide string manipulation;
16685 <!--page 361 -->
16686 <li> Functions for wide string date and time conversion; and
16687 <li> Functions that provide extended capabilities for conversion between multibyte and
16688 wide character sequences.
16689 </ul>
16691 Unless explicitly stated otherwise, if the execution of a function described in this
16692 subclause causes copying to take place between objects that overlap, the behavior is
16693 undefined.
16696 <p><small><a name="note277" href="#note277">277)</a> See ''future library directions'' (<a href="#7.26.12">7.26.12</a>).
16697 </small>
16698 <p><small><a name="note278" href="#note278">278)</a> wchar_t and wint_t can be the same integer type.
16699 </small>
16700 <p><small><a name="note279" href="#note279">279)</a> The value of the macro WEOF may differ from that of EOF and need not be negative.
16701 </small>
16703 <h4><a name="7.24.2" href="#7.24.2">7.24.2 Formatted wide character input/output functions</a></h4>
16705 The formatted wide character input/output functions shall behave as if there is a sequence
16706 point after the actions associated with each specifier.<sup><a href="#note280"><b>280)</b></a></sup>
16709 <p><small><a name="note280" href="#note280">280)</a> The fwprintf functions perform writes to memory for the %n specifier.
16710 </small>
16715 <pre>
16718 int fwprintf(FILE * restrict stream,
16719 const wchar_t * restrict format, ...);</pre>
16722 The fwprintf function writes output to the stream pointed to by stream, under
16723 control of the wide string pointed to by format that specifies how subsequent arguments
16724 are converted for output. If there are insufficient arguments for the format, the behavior
16725 is undefined. If the format is exhausted while arguments remain, the excess arguments
16726 are evaluated (as always) but are otherwise ignored. The fwprintf function returns
16727 when the end of the format string is encountered.
16729 The format is composed of zero or more directives: ordinary wide characters (not %),
16730 which are copied unchanged to the output stream; and conversion specifications, each of
16731 which results in fetching zero or more subsequent arguments, converting them, if
16732 applicable, according to the corresponding conversion specifier, and then writing the
16733 result to the output stream.
16735 Each conversion specification is introduced by the wide character %. After the %, the
16736 following appear in sequence:
16737 <ul>
16738 <li> Zero or more flags (in any order) that modify the meaning of the conversion
16739 specification.
16740 <li> An optional minimum field width. If the converted value has fewer wide characters
16741 than the field width, it is padded with spaces (by default) on the left (or right, if the
16744 <!--page 362 -->
16745 left adjustment flag, described later, has been given) to the field width. The field
16746 width takes the form of an asterisk * (described later) or a nonnegative decimal
16748 <li> An optional precision that gives the minimum number of digits to appear for the d, i,
16749 o, u, x, and X conversions, the number of digits to appear after the decimal-point
16750 wide character for a, A, e, E, f, and F conversions, the maximum number of
16751 significant digits for the g and G conversions, or the maximum number of wide
16752 characters to be written for s conversions. The precision takes the form of a period
16753 (.) followed either by an asterisk * (described later) or by an optional decimal
16754 integer; if only the period is specified, the precision is taken as zero. If a precision
16755 appears with any other conversion specifier, the behavior is undefined.
16756 <li> An optional length modifier that specifies the size of the argument.
16757 <li> A conversion specifier wide character that specifies the type of conversion to be
16758 applied.
16759 </ul>
16761 As noted above, a field width, or precision, or both, may be indicated by an asterisk. In
16762 this case, an int argument supplies the field width or precision. The arguments
16763 specifying field width, or precision, or both, shall appear (in that order) before the
16764 argument (if any) to be converted. A negative field width argument is taken as a - flag
16765 followed by a positive field width. A negative precision argument is taken as if the
16766 precision were omitted.
16768 The flag wide characters and their meanings are:
16769 - The result of the conversion is left-justified within the field. (It is right-justified if
16770 <pre>
16771 this flag is not specified.)</pre>
16772 + The result of a signed conversion always begins with a plus or minus sign. (It
16773 <pre>
16774 begins with a sign only when a negative value is converted if this flag is not
16776 space If the first wide character of a signed conversion is not a sign, or if a signed
16777 <pre>
16778 conversion results in no wide characters, a space is prefixed to the result. If the
16779 space and + flags both appear, the space flag is ignored.</pre>
16780 # The result is converted to an ''alternative form''. For o conversion, it increases
16781 <pre>
16782 the precision, if and only if necessary, to force the first digit of the result to be a
16786 <!--page 363 -->
16787 <pre>
16788 and G conversions, the result of converting a floating-point number always
16789 contains a decimal-point wide character, even if no digits follow it. (Normally, a
16790 decimal-point wide character appears in the result of these conversions only if a
16791 digit follows it.) For g and G conversions, trailing zeros are not removed from the
16792 result. For other conversions, the behavior is undefined.</pre>
16793 0 For d, i, o, u, x, X, a, A, e, E, f, F, g, and G conversions, leading zeros
16795 <pre>
16796 (following any indication of sign or base) are used to pad to the field width rather
16797 than performing space padding, except when converting an infinity or NaN. If the
16799 conversions, if a precision is specified, the 0 flag is ignored. For other
16800 conversions, the behavior is undefined.</pre>
16801 The length modifiers and their meanings are:
16802 hh Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
16803 <pre>
16804 signed char or unsigned char argument (the argument will have
16805 been promoted according to the integer promotions, but its value shall be
16806 converted to signed char or unsigned char before printing); or that
16807 a following n conversion specifier applies to a pointer to a signed char
16808 argument.</pre>
16809 h Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
16810 <pre>
16811 short int or unsigned short int argument (the argument will
16812 have been promoted according to the integer promotions, but its value shall
16813 be converted to short int or unsigned short int before printing);
16814 or that a following n conversion specifier applies to a pointer to a short
16815 int argument.</pre>
16816 l (ell) Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
16817 <pre>
16818 long int or unsigned long int argument; that a following n
16819 conversion specifier applies to a pointer to a long int argument; that a
16820 following c conversion specifier applies to a wint_t argument; that a
16821 following s conversion specifier applies to a pointer to a wchar_t
16822 argument; or has no effect on a following a, A, e, E, f, F, g, or G conversion
16823 specifier.</pre>
16824 ll (ell-ell) Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
16825 <pre>
16826 long long int or unsigned long long int argument; or that a
16827 following n conversion specifier applies to a pointer to a long long int
16828 argument.</pre>
16829 j Specifies that a following d, i, o, u, x, or X conversion specifier applies to
16830 <!--page 364 -->
16831 <pre>
16832 an intmax_t or uintmax_t argument; or that a following n conversion
16833 specifier applies to a pointer to an intmax_t argument.</pre>
16834 z Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
16835 <pre>
16836 size_t or the corresponding signed integer type argument; or that a
16837 following n conversion specifier applies to a pointer to a signed integer type
16838 corresponding to size_t argument.</pre>
16839 t Specifies that a following d, i, o, u, x, or X conversion specifier applies to a
16840 <pre>
16841 ptrdiff_t or the corresponding unsigned integer type argument; or that a
16842 following n conversion specifier applies to a pointer to a ptrdiff_t
16843 argument.</pre>
16844 L Specifies that a following a, A, e, E, f, F, g, or G conversion specifier
16845 <pre>
16846 applies to a long double argument.</pre>
16847 If a length modifier appears with any conversion specifier other than as specified above,
16848 the behavior is undefined.
16850 The conversion specifiers and their meanings are:
16851 d,i The int argument is converted to signed decimal in the style [-]dddd. The
16852 <pre>
16853 precision specifies the minimum number of digits to appear; if the value
16854 being converted can be represented in fewer digits, it is expanded with
16855 leading zeros. The default precision is 1. The result of converting a zero
16856 value with a precision of zero is no wide characters.</pre>
16857 o,u,x,X The unsigned int argument is converted to unsigned octal (o), unsigned
16858 <pre>
16859 decimal (u), or unsigned hexadecimal notation (x or X) in the style dddd; the
16860 letters abcdef are used for x conversion and the letters ABCDEF for X
16861 conversion. The precision specifies the minimum number of digits to appear;
16862 if the value being converted can be represented in fewer digits, it is expanded
16863 with leading zeros. The default precision is 1. The result of converting a
16864 zero value with a precision of zero is no wide characters.</pre>
16865 f,F A double argument representing a floating-point number is converted to
16866 <!--page 365 -->
16867 <pre>
16868 decimal notation in the style [-]ddd.ddd, where the number of digits after
16869 the decimal-point wide character is equal to the precision specification. If the
16870 precision is missing, it is taken as 6; if the precision is zero and the # flag is
16871 not specified, no decimal-point wide character appears. If a decimal-point
16872 wide character appears, at least one digit appears before it. The value is
16873 rounded to the appropriate number of digits.
16874 A double argument representing an infinity is converted in one of the styles
16875 [-]inf or [-]infinity -- which style is implementation-defined. A
16876 double argument representing a NaN is converted in one of the styles
16877 [-]nan or [-]nan(n-wchar-sequence) -- which style, and the meaning of
16878 any n-wchar-sequence, is implementation-defined. The F conversion
16879 specifier produces INF, INFINITY, or NAN instead of inf, infinity, or
16881 e,E A double argument representing a floating-point number is converted in the
16882 <pre>
16883 style [-]d.ddd e(+-)dd, where there is one digit (which is nonzero if the
16884 argument is nonzero) before the decimal-point wide character and the number
16885 of digits after it is equal to the precision; if the precision is missing, it is taken
16886 as 6; if the precision is zero and the # flag is not specified, no decimal-point
16887 wide character appears. The value is rounded to the appropriate number of
16888 digits. The E conversion specifier produces a number with E instead of e
16889 introducing the exponent. The exponent always contains at least two digits,
16890 and only as many more digits as necessary to represent the exponent. If the
16891 value is zero, the exponent is zero.
16892 A double argument representing an infinity or NaN is converted in the style
16893 of an f or F conversion specifier.</pre>
16894 g,G A double argument representing a floating-point number is converted in
16895 <pre>
16896 style f or e (or in style F or E in the case of a G conversion specifier),
16897 depending on the value converted and the precision. Let P equal the
16899 Then, if a conversion with style E would have an exponent of X :
16901 P - (X + 1).
16902 -- otherwise, the conversion is with style e (or E) and precision P - 1.
16903 Finally, unless the # flag is used, any trailing zeros are removed from the
16904 fractional portion of the result and the decimal-point wide character is
16905 removed if there is no fractional portion remaining.
16906 A double argument representing an infinity or NaN is converted in the style
16907 of an f or F conversion specifier.</pre>
16908 a,A A double argument representing a floating-point number is converted in the
16909 <pre>
16910 style [-]0xh.hhhh p(+-)d, where there is one hexadecimal digit (which is
16911 nonzero if the argument is a normalized floating-point number and is
16912 otherwise unspecified) before the decimal-point wide character<sup><a href="#note284"><b>284)</b></a></sup> and the
16913 number of hexadecimal digits after it is equal to the precision; if the precision
16917 <!--page 366 -->
16918 <pre>
16919 for an exact representation of the value; if the precision is missing and
16920 FLT_RADIX is not a power of 2, then the precision is sufficient to
16921 distinguish<sup><a href="#note285"><b>285)</b></a></sup> values of type double, except that trailing zeros may be
16922 omitted; if the precision is zero and the # flag is not specified, no decimal-
16923 point wide character appears. The letters abcdef are used for a conversion
16924 and the letters ABCDEF for A conversion. The A conversion specifier
16925 produces a number with X and P instead of x and p. The exponent always
16926 contains at least one digit, and only as many more digits as necessary to
16927 represent the decimal exponent of 2. If the value is zero, the exponent is
16928 zero.
16929 A double argument representing an infinity or NaN is converted in the style
16930 of an f or F conversion specifier.</pre>
16931 c If no l length modifier is present, the int argument is converted to a wide
16932 <pre>
16933 character as if by calling btowc and the resulting wide character is written.
16934 If an l length modifier is present, the wint_t argument is converted to
16935 wchar_t and written.</pre>
16936 s If no l length modifier is present, the argument shall be a pointer to the initial
16937 <pre>
16938 element of a character array containing a multibyte character sequence
16939 beginning in the initial shift state. Characters from the array are converted as
16940 if by repeated calls to the mbrtowc function, with the conversion state
16941 described by an mbstate_t object initialized to zero before the first
16942 multibyte character is converted, and written up to (but not including) the
16943 terminating null wide character. If the precision is specified, no more than
16944 that many wide characters are written. If the precision is not specified or is
16945 greater than the size of the converted array, the converted array shall contain a
16946 null wide character.
16947 If an l length modifier is present, the argument shall be a pointer to the initial
16948 element of an array of wchar_t type. Wide characters from the array are
16949 written up to (but not including) a terminating null wide character. If the
16950 precision is specified, no more than that many wide characters are written. If
16951 the precision is not specified or is greater than the size of the array, the array
16952 shall contain a null wide character.</pre>
16953 p The argument shall be a pointer to void. The value of the pointer is
16954 <pre>
16955 converted to a sequence of printing wide characters, in an implementation-</pre>
16957 <!--page 367 -->
16958 <pre>
16959 defined manner.</pre>
16960 n The argument shall be a pointer to signed integer into which is written the
16961 <pre>
16962 number of wide characters written to the output stream so far by this call to
16963 fwprintf. No argument is converted, but one is consumed. If the
16964 conversion specification includes any flags, a field width, or a precision, the
16965 behavior is undefined.</pre>
16966 % A % wide character is written. No argument is converted. The complete
16968 <pre>
16969 conversion specification shall be %%.</pre>
16970 If a conversion specification is invalid, the behavior is undefined.<sup><a href="#note286"><b>286)</b></a></sup> If any argument is
16971 not the correct type for the corresponding conversion specification, the behavior is
16972 undefined.
16974 In no case does a nonexistent or small field width cause truncation of a field; if the result
16975 of a conversion is wider than the field width, the field is expanded to contain the
16976 conversion result.
16978 For a and A conversions, if FLT_RADIX is a power of 2, the value is correctly rounded
16979 to a hexadecimal floating number with the given precision.
16980 Recommended practice
16982 For a and A conversions, if FLT_RADIX is not a power of 2 and the result is not exactly
16983 representable in the given precision, the result should be one of the two adjacent numbers
16984 in hexadecimal floating style with the given precision, with the extra stipulation that the
16985 error should have a correct sign for the current rounding direction.
16987 For e, E, f, F, g, and G conversions, if the number of significant decimal digits is at most
16988 DECIMAL_DIG, then the result should be correctly rounded.<sup><a href="#note287"><b>287)</b></a></sup> If the number of
16989 significant decimal digits is more than DECIMAL_DIG but the source value is exactly
16990 representable with DECIMAL_DIG digits, then the result should be an exact
16991 representation with trailing zeros. Otherwise, the source value is bounded by two
16992 adjacent decimal strings L < U, both having DECIMAL_DIG significant digits; the value
16993 of the resultant decimal string D should satisfy L <= D <= U, with the extra stipulation that
16994 the error should have a correct sign for the current rounding direction.
16997 The fwprintf function returns the number of wide characters transmitted, or a negative
16998 value if an output or encoding error occurred.
17000 <!--page 368 -->
17001 Environmental limits
17003 The number of wide characters that can be produced by any single conversion shall be at
17004 least 4095.
17006 EXAMPLE To print a date and time in the form ''Sunday, July 3, 10:02'' followed by pi to five decimal
17007 places:
17008 <pre>
17012 /* ... */
17013 wchar_t *weekday, *month; // pointers to wide strings
17014 int day, hour, min;
17015 fwprintf(stdout, L"%ls, %ls %d, %.2d:%.2d\n",
17016 weekday, month, day, hour, min);
17019 <p><b> Forward references</b>: the btowc function (<a href="#7.24.6.1.1">7.24.6.1.1</a>), the mbrtowc function
17023 <p><small><a name="note281" href="#note281">281)</a> Note that 0 is taken as a flag, not as the beginning of a field width.
17024 </small>
17025 <p><small><a name="note282" href="#note282">282)</a> The results of all floating conversions of a negative zero, and of negative values that round to zero,
17026 include a minus sign.
17027 </small>
17028 <p><small><a name="note283" href="#note283">283)</a> When applied to infinite and NaN values, the -, +, and space flag wide characters have their usual
17029 meaning; the # and 0 flag wide characters have no effect.
17030 </small>
17031 <p><small><a name="note284" href="#note284">284)</a> Binary implementations can choose the hexadecimal digit to the left of the decimal-point wide
17032 character so that subsequent digits align to nibble (4-bit) boundaries.
17033 </small>
17034 <p><small><a name="note285" href="#note285">285)</a> The precision p is sufficient to distinguish values of the source type if 16 p-1 > b n where b is
17035 FLT_RADIX and n is the number of base-b digits in the significand of the source type. A smaller p
17036 might suffice depending on the implementation's scheme for determining the digit to the left of the
17037 decimal-point wide character.
17038 </small>
17039 <p><small><a name="note286" href="#note286">286)</a> See ''future library directions'' (<a href="#7.26.12">7.26.12</a>).
17040 </small>
17041 <p><small><a name="note287" href="#note287">287)</a> For binary-to-decimal conversion, the result format's values are the numbers representable with the
17042 given format specifier. The number of significant digits is determined by the format specifier, and in
17043 the case of fixed-point conversion by the source value as well.
17044 </small>
17049 <pre>
17052 int fwscanf(FILE * restrict stream,
17053 const wchar_t * restrict format, ...);</pre>
17056 The fwscanf function reads input from the stream pointed to by stream, under
17057 control of the wide string pointed to by format that specifies the admissible input
17058 sequences and how they are to be converted for assignment, using subsequent arguments
17059 as pointers to the objects to receive the converted input. If there are insufficient
17060 arguments for the format, the behavior is undefined. If the format is exhausted while
17061 arguments remain, the excess arguments are evaluated (as always) but are otherwise
17062 ignored.
17064 The format is composed of zero or more directives: one or more white-space wide
17065 characters, an ordinary wide character (neither % nor a white-space wide character), or a
17066 conversion specification. Each conversion specification is introduced by the wide
17067 character %. After the %, the following appear in sequence:
17068 <ul>
17069 <li> An optional assignment-suppressing wide character *.
17070 <li> An optional decimal integer greater than zero that specifies the maximum field width
17071 (in wide characters).
17072 <!--page 369 -->
17073 <li> An optional length modifier that specifies the size of the receiving object.
17074 <li> A conversion specifier wide character that specifies the type of conversion to be
17075 applied.
17076 </ul>
17078 The fwscanf function executes each directive of the format in turn. If a directive fails,
17079 as detailed below, the function returns. Failures are described as input failures (due to the
17080 occurrence of an encoding error or the unavailability of input characters), or matching
17081 failures (due to inappropriate input).
17083 A directive composed of white-space wide character(s) is executed by reading input up to
17084 the first non-white-space wide character (which remains unread), or until no more wide
17085 characters can be read.
17087 A directive that is an ordinary wide character is executed by reading the next wide
17088 character of the stream. If that wide character differs from the directive, the directive
17089 fails and the differing and subsequent wide characters remain unread. Similarly, if end-
17090 of-file, an encoding error, or a read error prevents a wide character from being read, the
17091 directive fails.
17093 A directive that is a conversion specification defines a set of matching input sequences, as
17094 described below for each specifier. A conversion specification is executed in the
17095 following steps:
17097 Input white-space wide characters (as specified by the iswspace function) are skipped,
17098 unless the specification includes a [, c, or n specifier.<sup><a href="#note288"><b>288)</b></a></sup>
17100 An input item is read from the stream, unless the specification includes an n specifier. An
17101 input item is defined as the longest sequence of input wide characters which does not
17102 exceed any specified field width and which is, or is a prefix of, a matching input
17103 sequence.<sup><a href="#note289"><b>289)</b></a></sup> The first wide character, if any, after the input item remains unread. If the
17104 length of the input item is zero, the execution of the directive fails; this condition is a
17105 matching failure unless end-of-file, an encoding error, or a read error prevented input
17106 from the stream, in which case it is an input failure.
17108 Except in the case of a % specifier, the input item (or, in the case of a %n directive, the
17109 count of input wide characters) is converted to a type appropriate to the conversion
17110 specifier. If the input item is not a matching sequence, the execution of the directive fails:
17111 this condition is a matching failure. Unless assignment suppression was indicated by a *,
17112 the result of the conversion is placed in the object pointed to by the first argument
17113 following the format argument that has not already received a conversion result. If this
17116 <!--page 370 -->
17117 object does not have an appropriate type, or if the result of the conversion cannot be
17118 represented in the object, the behavior is undefined.
17120 The length modifiers and their meanings are:
17121 hh Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
17122 <pre>
17123 to an argument with type pointer to signed char or unsigned char.</pre>
17124 h Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
17125 <pre>
17126 to an argument with type pointer to short int or unsigned short
17127 int.</pre>
17128 l (ell) Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
17129 <pre>
17130 to an argument with type pointer to long int or unsigned long
17131 int; that a following a, A, e, E, f, F, g, or G conversion specifier applies to
17132 an argument with type pointer to double; or that a following c, s, or [
17133 conversion specifier applies to an argument with type pointer to wchar_t.</pre>
17134 ll (ell-ell) Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
17135 <pre>
17136 to an argument with type pointer to long long int or unsigned
17137 long long int.</pre>
17138 j Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
17139 <pre>
17140 to an argument with type pointer to intmax_t or uintmax_t.</pre>
17141 z Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
17142 <pre>
17143 to an argument with type pointer to size_t or the corresponding signed
17144 integer type.</pre>
17145 t Specifies that a following d, i, o, u, x, X, or n conversion specifier applies
17146 <pre>
17147 to an argument with type pointer to ptrdiff_t or the corresponding
17148 unsigned integer type.</pre>
17149 L Specifies that a following a, A, e, E, f, F, g, or G conversion specifier
17150 <pre>
17151 applies to an argument with type pointer to long double.</pre>
17152 If a length modifier appears with any conversion specifier other than as specified above,
17153 the behavior is undefined.
17155 The conversion specifiers and their meanings are:
17156 d Matches an optionally signed decimal integer, whose format is the same as
17157 <pre>
17158 expected for the subject sequence of the wcstol function with the value 10
17159 for the base argument. The corresponding argument shall be a pointer to
17160 signed integer.</pre>
17161 i Matches an optionally signed integer, whose format is the same as expected
17162 <!--page 371 -->
17163 <pre>
17164 for the subject sequence of the wcstol function with the value 0 for the
17165 base argument. The corresponding argument shall be a pointer to signed
17166 integer.</pre>
17167 o Matches an optionally signed octal integer, whose format is the same as
17168 <pre>
17169 expected for the subject sequence of the wcstoul function with the value 8
17170 for the base argument. The corresponding argument shall be a pointer to
17171 unsigned integer.</pre>
17172 u Matches an optionally signed decimal integer, whose format is the same as
17173 <pre>
17174 expected for the subject sequence of the wcstoul function with the value 10
17175 for the base argument. The corresponding argument shall be a pointer to
17176 unsigned integer.</pre>
17177 x Matches an optionally signed hexadecimal integer, whose format is the same
17178 <pre>
17179 as expected for the subject sequence of the wcstoul function with the value
17180 16 for the base argument. The corresponding argument shall be a pointer to
17181 unsigned integer.</pre>
17182 a,e,f,g Matches an optionally signed floating-point number, infinity, or NaN, whose
17183 <pre>
17184 format is the same as expected for the subject sequence of the wcstod
17185 function. The corresponding argument shall be a pointer to floating.</pre>
17186 c Matches a sequence of wide characters of exactly the number specified by the
17187 <pre>
17188 field width (1 if no field width is present in the directive).
17189 If no l length modifier is present, characters from the input field are
17190 converted as if by repeated calls to the wcrtomb function, with the
17191 conversion state described by an mbstate_t object initialized to zero
17192 before the first wide character is converted. The corresponding argument
17193 shall be a pointer to the initial element of a character array large enough to
17194 accept the sequence. No null character is added.
17195 If an l length modifier is present, the corresponding argument shall be a
17196 pointer to the initial element of an array of wchar_t large enough to accept
17197 the sequence. No null wide character is added.</pre>
17198 s Matches a sequence of non-white-space wide characters.
17199 <!--page 372 -->
17200 <pre>
17201 If no l length modifier is present, characters from the input field are
17202 converted as if by repeated calls to the wcrtomb function, with the
17203 conversion state described by an mbstate_t object initialized to zero
17204 before the first wide character is converted. The corresponding argument
17205 shall be a pointer to the initial element of a character array large enough to
17206 accept the sequence and a terminating null character, which will be added
17207 automatically.
17208 If an l length modifier is present, the corresponding argument shall be a
17209 pointer to the initial element of an array of wchar_t large enough to accept
17210 the sequence and the terminating null wide character, which will be added
17211 automatically.</pre>
17212 [ Matches a nonempty sequence of wide characters from a set of expected
17213 <pre>
17214 characters (the scanset).
17215 If no l length modifier is present, characters from the input field are
17216 converted as if by repeated calls to the wcrtomb function, with the
17217 conversion state described by an mbstate_t object initialized to zero
17218 before the first wide character is converted. The corresponding argument
17219 shall be a pointer to the initial element of a character array large enough to
17220 accept the sequence and a terminating null character, which will be added
17221 automatically.
17222 If an l length modifier is present, the corresponding argument shall be a
17223 pointer to the initial element of an array of wchar_t large enough to accept
17224 the sequence and the terminating null wide character, which will be added
17225 automatically.
17226 The conversion specifier includes all subsequent wide characters in the
17227 format string, up to and including the matching right bracket (]). The wide
17228 characters between the brackets (the scanlist) compose the scanset, unless the
17229 wide character after the left bracket is a circumflex (^), in which case the
17230 scanset contains all wide characters that do not appear in the scanlist between
17231 the circumflex and the right bracket. If the conversion specifier begins with
17232 [] or [^], the right bracket wide character is in the scanlist and the next
17233 following right bracket wide character is the matching right bracket that ends
17234 the specification; otherwise the first following right bracket wide character is
17235 the one that ends the specification. If a - wide character is in the scanlist and
17236 is not the first, nor the second where the first wide character is a ^, nor the
17237 last character, the behavior is implementation-defined.</pre>
17238 p Matches an implementation-defined set of sequences, which should be the
17239 <pre>
17240 same as the set of sequences that may be produced by the %p conversion of
17241 the fwprintf function. The corresponding argument shall be a pointer to a
17242 pointer to void. The input item is converted to a pointer value in an
17243 implementation-defined manner. If the input item is a value converted earlier
17244 during the same program execution, the pointer that results shall compare
17245 equal to that value; otherwise the behavior of the %p conversion is undefined.</pre>
17246 n No input is consumed. The corresponding argument shall be a pointer to
17247 <!--page 373 -->
17248 <pre>
17249 signed integer into which is to be written the number of wide characters read
17250 from the input stream so far by this call to the fwscanf function. Execution
17251 of a %n directive does not increment the assignment count returned at the
17252 completion of execution of the fwscanf function. No argument is
17253 converted, but one is consumed. If the conversion specification includes an
17254 assignment-suppressing wide character or a field width, the behavior is
17255 undefined.</pre>
17256 % Matches a single % wide character; no conversion or assignment occurs. The
17258 <pre>
17259 complete conversion specification shall be %%.</pre>
17260 If a conversion specification is invalid, the behavior is undefined.<sup><a href="#note290"><b>290)</b></a></sup>
17262 The conversion specifiers A, E, F, G, and X are also valid and behave the same as,
17263 respectively, a, e, f, g, and x.
17265 Trailing white space (including new-line wide characters) is left unread unless matched
17266 by a directive. The success of literal matches and suppressed assignments is not directly
17267 determinable other than via the %n directive.
17270 The fwscanf function returns the value of the macro EOF if an input failure occurs
17271 before any conversion. Otherwise, the function returns the number of input items
17272 assigned, which can be fewer than provided for, or even zero, in the event of an early
17273 matching failure.
17275 EXAMPLE 1 The call:
17276 <pre>
17279 /* ... */
17280 int n, i; float x; wchar_t name[50];
17282 with the input line:
17283 <pre>
17285 will assign to n the value 3, to i the value 25, to x the value 5.432, and to name the sequence
17286 thompson\0.
17289 EXAMPLE 2 The call:
17290 <pre>
17293 /* ... */
17294 int i; float x; double y;
17296 with input:
17297 <pre>
17299 will assign to i the value 56 and to x the value 789.0, will skip past 0123, and will assign to y the value
17300 56.0. The next wide character read from the input stream will be a.
17303 <!--page 374 -->
17304 <p><b> Forward references</b>: the wcstod, wcstof, and wcstold functions (<a href="#7.24.4.1.1">7.24.4.1.1</a>), the
17305 wcstol, wcstoll, wcstoul, and wcstoull functions (<a href="#7.24.4.1.2">7.24.4.1.2</a>), the wcrtomb
17309 <p><small><a name="note288" href="#note288">288)</a> These white-space wide characters are not counted against a specified field width.
17310 </small>
17311 <p><small><a name="note289" href="#note289">289)</a> fwscanf pushes back at most one input wide character onto the input stream. Therefore, some
17312 sequences that are acceptable to wcstod, wcstol, etc., are unacceptable to fwscanf.
17313 </small>
17314 <p><small><a name="note290" href="#note290">290)</a> See ''future library directions'' (<a href="#7.26.12">7.26.12</a>).
17315 </small>
17320 <pre>
17322 int swprintf(wchar_t * restrict s,
17323 size_t n,
17324 const wchar_t * restrict format, ...);</pre>
17327 The swprintf function is equivalent to fwprintf, except that the argument s
17328 specifies an array of wide characters into which the generated output is to be written,
17329 rather than written to a stream. No more than n wide characters are written, including a
17330 terminating null wide character, which is always added (unless n is zero).
17333 The swprintf function returns the number of wide characters written in the array, not
17334 counting the terminating null wide character, or a negative value if an encoding error
17335 occurred or if n or more wide characters were requested to be written.
17340 <pre>
17342 int swscanf(const wchar_t * restrict s,
17343 const wchar_t * restrict format, ...);</pre>
17346 The swscanf function is equivalent to fwscanf, except that the argument s specifies a
17347 wide string from which the input is to be obtained, rather than from a stream. Reaching
17348 the end of the wide string is equivalent to encountering end-of-file for the fwscanf
17349 function.
17352 The swscanf function returns the value of the macro EOF if an input failure occurs
17353 before any conversion. Otherwise, the swscanf function returns the number of input
17354 items assigned, which can be fewer than provided for, or even zero, in the event of an
17355 early matching failure.
17356 <!--page 375 -->
17361 <pre>
17365 int vfwprintf(FILE * restrict stream,
17366 const wchar_t * restrict format,
17367 va_list arg);</pre>
17370 The vfwprintf function is equivalent to fwprintf, with the variable argument list
17371 replaced by arg, which shall have been initialized by the va_start macro (and
17372 possibly subsequent va_arg calls). The vfwprintf function does not invoke the
17376 The vfwprintf function returns the number of wide characters transmitted, or a
17377 negative value if an output or encoding error occurred.
17379 EXAMPLE The following shows the use of the vfwprintf function in a general error-reporting
17380 routine.
17381 <pre>
17385 void error(char *function_name, wchar_t *format, ...)
17386 {
17387 va_list args;
17388 va_start(args, format);
17389 // print out name of function causing error
17390 fwprintf(stderr, L"ERROR in %s: ", function_name);
17391 // print out remainder of message
17392 vfwprintf(stderr, format, args);
17393 va_end(args);
17394 }</pre>
17399 <!--page 376 -->
17402 <p><small><a name="note291" href="#note291">291)</a> As the functions vfwprintf, vswprintf, vfwscanf, vwprintf, vwscanf, and vswscanf
17403 invoke the va_arg macro, the value of arg after the return is indeterminate.
17404 </small>
17409 <pre>
17413 int vfwscanf(FILE * restrict stream,
17414 const wchar_t * restrict format,
17415 va_list arg);</pre>
17418 The vfwscanf function is equivalent to fwscanf, with the variable argument list
17419 replaced by arg, which shall have been initialized by the va_start macro (and
17420 possibly subsequent va_arg calls). The vfwscanf function does not invoke the
17421 va_end macro.291)
17424 The vfwscanf function returns the value of the macro EOF if an input failure occurs
17425 before any conversion. Otherwise, the vfwscanf function returns the number of input
17426 items assigned, which can be fewer than provided for, or even zero, in the event of an
17427 early matching failure.
17432 <pre>
17435 int vswprintf(wchar_t * restrict s,
17436 size_t n,
17437 const wchar_t * restrict format,
17438 va_list arg);</pre>
17441 The vswprintf function is equivalent to swprintf, with the variable argument list
17442 replaced by arg, which shall have been initialized by the va_start macro (and
17443 possibly subsequent va_arg calls). The vswprintf function does not invoke the
17444 va_end macro.291)
17447 The vswprintf function returns the number of wide characters written in the array, not
17448 counting the terminating null wide character, or a negative value if an encoding error
17449 occurred or if n or more wide characters were requested to be generated.
17450 <!--page 377 -->
17455 <pre>
17458 int vswscanf(const wchar_t * restrict s,
17459 const wchar_t * restrict format,
17460 va_list arg);</pre>
17463 The vswscanf function is equivalent to swscanf, with the variable argument list
17464 replaced by arg, which shall have been initialized by the va_start macro (and
17465 possibly subsequent va_arg calls). The vswscanf function does not invoke the
17466 va_end macro.291)
17469 The vswscanf function returns the value of the macro EOF if an input failure occurs
17470 before any conversion. Otherwise, the vswscanf function returns the number of input
17471 items assigned, which can be fewer than provided for, or even zero, in the event of an
17472 early matching failure.
17477 <pre>
17480 int vwprintf(const wchar_t * restrict format,
17481 va_list arg);</pre>
17484 The vwprintf function is equivalent to wprintf, with the variable argument list
17485 replaced by arg, which shall have been initialized by the va_start macro (and
17486 possibly subsequent va_arg calls). The vwprintf function does not invoke the
17487 va_end macro.291)
17490 The vwprintf function returns the number of wide characters transmitted, or a negative
17491 value if an output or encoding error occurred.
17492 <!--page 378 -->
17497 <pre>
17500 int vwscanf(const wchar_t * restrict format,
17501 va_list arg);</pre>
17504 The vwscanf function is equivalent to wscanf, with the variable argument list
17505 replaced by arg, which shall have been initialized by the va_start macro (and
17506 possibly subsequent va_arg calls). The vwscanf function does not invoke the
17507 va_end macro.291)
17510 The vwscanf function returns the value of the macro EOF if an input failure occurs
17511 before any conversion. Otherwise, the vwscanf function returns the number of input
17512 items assigned, which can be fewer than provided for, or even zero, in the event of an
17513 early matching failure.
17518 <pre>
17520 int wprintf(const wchar_t * restrict format, ...);</pre>
17523 The wprintf function is equivalent to fwprintf with the argument stdout
17524 interposed before the arguments to wprintf.
17527 The wprintf function returns the number of wide characters transmitted, or a negative
17528 value if an output or encoding error occurred.
17533 <pre>
17535 int wscanf(const wchar_t * restrict format, ...);</pre>
17538 The wscanf function is equivalent to fwscanf with the argument stdin interposed
17539 before the arguments to wscanf.
17540 <!--page 379 -->
17543 The wscanf function returns the value of the macro EOF if an input failure occurs
17544 before any conversion. Otherwise, the wscanf function returns the number of input
17545 items assigned, which can be fewer than provided for, or even zero, in the event of an
17546 early matching failure.
17553 <pre>
17556 wint_t fgetwc(FILE *stream);</pre>
17559 If the end-of-file indicator for the input stream pointed to by stream is not set and a
17560 next wide character is present, the fgetwc function obtains that wide character as a
17561 wchar_t converted to a wint_t and advances the associated file position indicator for
17562 the stream (if defined).
17565 If the end-of-file indicator for the stream is set, or if the stream is at end-of-file, the end-
17566 of-file indicator for the stream is set and the fgetwc function returns WEOF. Otherwise,
17567 the fgetwc function returns the next wide character from the input stream pointed to by
17568 stream. If a read error occurs, the error indicator for the stream is set and the fgetwc
17569 function returns WEOF. If an encoding error occurs (including too few bytes), the value of
17570 the macro EILSEQ is stored in errno and the fgetwc function returns WEOF.<sup><a href="#note292"><b>292)</b></a></sup>
17573 <p><small><a name="note292" href="#note292">292)</a> An end-of-file and a read error can be distinguished by use of the feof and ferror functions.
17574 Also, errno will be set to EILSEQ by input/output functions only if an encoding error occurs.
17575 </small>
17580 <pre>
17583 wchar_t *fgetws(wchar_t * restrict s,
17584 int n, FILE * restrict stream);</pre>
17587 The fgetws function reads at most one less than the number of wide characters
17588 specified by n from the stream pointed to by stream into the array pointed to by s. No
17591 <!--page 380 -->
17592 additional wide characters are read after a new-line wide character (which is retained) or
17593 after end-of-file. A null wide character is written immediately after the last wide
17594 character read into the array.
17597 The fgetws function returns s if successful. If end-of-file is encountered and no
17598 characters have been read into the array, the contents of the array remain unchanged and a
17599 null pointer is returned. If a read or encoding error occurs during the operation, the array
17600 contents are indeterminate and a null pointer is returned.
17605 <pre>
17608 wint_t fputwc(wchar_t c, FILE *stream);</pre>
17611 The fputwc function writes the wide character specified by c to the output stream
17612 pointed to by stream, at the position indicated by the associated file position indicator
17613 for the stream (if defined), and advances the indicator appropriately. If the file cannot
17614 support positioning requests, or if the stream was opened with append mode, the
17615 character is appended to the output stream.
17618 The fputwc function returns the wide character written. If a write error occurs, the
17619 error indicator for the stream is set and fputwc returns WEOF. If an encoding error
17620 occurs, the value of the macro EILSEQ is stored in errno and fputwc returns WEOF.
17625 <pre>
17628 int fputws(const wchar_t * restrict s,
17629 FILE * restrict stream);</pre>
17632 The fputws function writes the wide string pointed to by s to the stream pointed to by
17633 stream. The terminating null wide character is not written.
17636 The fputws function returns EOF if a write or encoding error occurs; otherwise, it
17637 returns a nonnegative value.
17638 <!--page 381 -->
17643 <pre>
17646 int fwide(FILE *stream, int mode);</pre>
17649 The fwide function determines the orientation of the stream pointed to by stream. If
17650 mode is greater than zero, the function first attempts to make the stream wide oriented. If
17651 mode is less than zero, the function first attempts to make the stream byte oriented.<sup><a href="#note293"><b>293)</b></a></sup>
17652 Otherwise, mode is zero and the function does not alter the orientation of the stream.
17655 The fwide function returns a value greater than zero if, after the call, the stream has
17656 wide orientation, a value less than zero if the stream has byte orientation, or zero if the
17657 stream has no orientation.
17660 <p><small><a name="note293" href="#note293">293)</a> If the orientation of the stream has already been determined, fwide does not change it.
17661 </small>
17666 <pre>
17669 wint_t getwc(FILE *stream);</pre>
17672 The getwc function is equivalent to fgetwc, except that if it is implemented as a
17673 macro, it may evaluate stream more than once, so the argument should never be an
17674 expression with side effects.
17677 The getwc function returns the next wide character from the input stream pointed to by
17678 stream, or WEOF.
17683 <pre>
17685 wint_t getwchar(void);</pre>
17690 <!--page 382 -->
17693 The getwchar function is equivalent to getwc with the argument stdin.
17696 The getwchar function returns the next wide character from the input stream pointed to
17697 by stdin, or WEOF.
17702 <pre>
17705 wint_t putwc(wchar_t c, FILE *stream);</pre>
17708 The putwc function is equivalent to fputwc, except that if it is implemented as a
17709 macro, it may evaluate stream more than once, so that argument should never be an
17710 expression with side effects.
17713 The putwc function returns the wide character written, or WEOF.
17718 <pre>
17720 wint_t putwchar(wchar_t c);</pre>
17723 The putwchar function is equivalent to putwc with the second argument stdout.
17726 The putwchar function returns the character written, or WEOF.
17731 <pre>
17734 wint_t ungetwc(wint_t c, FILE *stream);</pre>
17737 The ungetwc function pushes the wide character specified by c back onto the input
17738 stream pointed to by stream. Pushed-back wide characters will be returned by
17739 subsequent reads on that stream in the reverse order of their pushing. A successful
17740 <!--page 383 -->
17741 intervening call (with the stream pointed to by stream) to a file positioning function
17742 (fseek, fsetpos, or rewind) discards any pushed-back wide characters for the
17743 stream. The external storage corresponding to the stream is unchanged.
17745 One wide character of pushback is guaranteed, even if the call to the ungetwc function
17746 follows just after a call to a formatted wide character input function fwscanf,
17747 vfwscanf, vwscanf, or wscanf. If the ungetwc function is called too many times
17748 on the same stream without an intervening read or file positioning operation on that
17749 stream, the operation may fail.
17751 If the value of c equals that of the macro WEOF, the operation fails and the input stream is
17752 unchanged.
17754 A successful call to the ungetwc function clears the end-of-file indicator for the stream.
17755 The value of the file position indicator for the stream after reading or discarding all
17756 pushed-back wide characters is the same as it was before the wide characters were pushed
17757 back. For a text or binary stream, the value of its file position indicator after a successful
17758 call to the ungetwc function is unspecified until all pushed-back wide characters are
17759 read or discarded.
17762 The ungetwc function returns the wide character pushed back, or WEOF if the operation
17763 fails.
17767 The header <a href="#7.24"><wchar.h></a> declares a number of functions useful for wide string
17768 manipulation. Various methods are used for determining the lengths of the arrays, but in
17769 all cases a wchar_t * argument points to the initial (lowest addressed) element of the
17770 array. If an array is accessed beyond the end of an object, the behavior is undefined.
17772 Where an argument declared as size_t n determines the length of the array for a
17773 function, n can have the value zero on a call to that function. Unless explicitly stated
17774 otherwise in the description of a particular function in this subclause, pointer arguments
17775 on such a call shall still have valid values, as described in <a href="#7.1.4">7.1.4</a>. On such a call, a
17776 function that locates a wide character finds no occurrence, a function that compares two
17777 wide character sequences returns zero, and a function that copies wide characters copies
17778 zero wide characters.
17779 <!--page 384 -->
17781 <h5><a name="7.24.4.1" href="#7.24.4.1">7.24.4.1 Wide string numeric conversion functions</a></h5>
17783 <h5><a name="7.24.4.1.1" href="#7.24.4.1.1">7.24.4.1.1 The wcstod, wcstof, and wcstold functions</a></h5>
17786 <pre>
17788 double wcstod(const wchar_t * restrict nptr,
17789 wchar_t ** restrict endptr);
17790 float wcstof(const wchar_t * restrict nptr,
17791 wchar_t ** restrict endptr);
17792 long double wcstold(const wchar_t * restrict nptr,
17793 wchar_t ** restrict endptr);</pre>
17796 The wcstod, wcstof, and wcstold functions convert the initial portion of the wide
17797 string pointed to by nptr to double, float, and long double representation,
17798 respectively. First, they decompose the input string into three parts: an initial, possibly
17799 empty, sequence of white-space wide characters (as specified by the iswspace
17800 function), a subject sequence resembling a floating-point constant or representing an
17801 infinity or NaN; and a final wide string of one or more unrecognized wide characters,
17802 including the terminating null wide character of the input wide string. Then, they attempt
17803 to convert the subject sequence to a floating-point number, and return the result.
17805 The expected form of the subject sequence is an optional plus or minus sign, then one of
17806 the following:
17807 <ul>
17808 <li> a nonempty sequence of decimal digits optionally containing a decimal-point wide
17809 character, then an optional exponent part as defined for the corresponding single-byte
17812 decimal-point wide character, then an optional binary exponent part as defined in
17814 <li> INF or INFINITY, or any other wide string equivalent except for case
17815 <li> NAN or NAN(n-wchar-sequenceopt), or any other wide string equivalent except for
17816 case in the NAN part, where:
17817 <pre>
17818 n-wchar-sequence:
17819 digit
17820 nondigit
17821 n-wchar-sequence digit
17822 n-wchar-sequence nondigit</pre>
17823 </ul>
17824 The subject sequence is defined as the longest initial subsequence of the input wide
17825 string, starting with the first non-white-space wide character, that is of the expected form.
17826 <!--page 385 -->
17827 The subject sequence contains no wide characters if the input wide string is not of the
17828 expected form.
17830 If the subject sequence has the expected form for a floating-point number, the sequence of
17831 wide characters starting with the first digit or the decimal-point wide character
17832 (whichever occurs first) is interpreted as a floating constant according to the rules of
17833 <a href="#6.4.4.2">6.4.4.2</a>, except that the decimal-point wide character is used in place of a period, and that
17834 if neither an exponent part nor a decimal-point wide character appears in a decimal
17835 floating point number, or if a binary exponent part does not appear in a hexadecimal
17836 floating point number, an exponent part of the appropriate type with value zero is
17837 assumed to follow the last digit in the string. If the subject sequence begins with a minus
17838 sign, the sequence is interpreted as negated.<sup><a href="#note294"><b>294)</b></a></sup> A wide character sequence INF or
17839 INFINITY is interpreted as an infinity, if representable in the return type, else like a
17840 floating constant that is too large for the range of the return type. A wide character
17841 sequence NAN or NAN(n-wchar-sequenceopt) is interpreted as a quiet NaN, if supported
17842 in the return type, else like a subject sequence part that does not have the expected form;
17843 the meaning of the n-wchar sequences is implementation-defined.<sup><a href="#note295"><b>295)</b></a></sup> A pointer to the
17844 final wide string is stored in the object pointed to by endptr, provided that endptr is
17845 not a null pointer.
17847 If the subject sequence has the hexadecimal form and FLT_RADIX is a power of 2, the
17848 value resulting from the conversion is correctly rounded.
17850 In other than the "C" locale, additional locale-specific subject sequence forms may be
17851 accepted.
17853 If the subject sequence is empty or does not have the expected form, no conversion is
17854 performed; the value of nptr is stored in the object pointed to by endptr, provided
17855 that endptr is not a null pointer.
17856 Recommended practice
17858 If the subject sequence has the hexadecimal form, FLT_RADIX is not a power of 2, and
17859 the result is not exactly representable, the result should be one of the two numbers in the
17860 appropriate internal format that are adjacent to the hexadecimal floating source value,
17861 with the extra stipulation that the error should have a correct sign for the current rounding
17862 direction.
17866 <!--page 386 -->
17868 If the subject sequence has the decimal form and at most DECIMAL_DIG (defined in
17869 <a href="#7.7"><float.h></a>) significant digits, the result should be correctly rounded. If the subject
17870 sequence D has the decimal form and more than DECIMAL_DIG significant digits,
17871 consider the two bounding, adjacent decimal strings L and U, both having
17872 DECIMAL_DIG significant digits, such that the values of L, D, and U satisfy L <= D <= U.
17873 The result should be one of the (equal or adjacent) values that would be obtained by
17874 correctly rounding L and U according to the current rounding direction, with the extra
17875 stipulation that the error with respect to D should have a correct sign for the current
17879 The functions return the converted value, if any. If no conversion could be performed,
17880 zero is returned. If the correct value is outside the range of representable values, plus or
17881 minus HUGE_VAL, HUGE_VALF, or HUGE_VALL is returned (according to the return
17882 type and sign of the value), and the value of the macro ERANGE is stored in errno. If
17883 the result underflows (<a href="#7.12.1">7.12.1</a>), the functions return a value whose magnitude is no greater
17884 than the smallest normalized positive number in the return type; whether errno acquires
17885 the value ERANGE is implementation-defined.
17890 <!--page 387 -->
17893 <p><small><a name="note294" href="#note294">294)</a> It is unspecified whether a minus-signed sequence is converted to a negative number directly or by
17894 negating the value resulting from converting the corresponding unsigned sequence (see <a href="#F.5">F.5</a>); the two
17895 methods may yield different results if rounding is toward positive or negative infinity. In either case,
17896 the functions honor the sign of zero if floating-point arithmetic supports signed zeros.
17897 </small>
17898 <p><small><a name="note295" href="#note295">295)</a> An implementation may use the n-wchar sequence to determine extra information to be represented in
17899 the NaN's significand.
17900 </small>
17901 <p><small><a name="note296" href="#note296">296)</a> DECIMAL_DIG, defined in <a href="#7.7"><float.h></a>, should be sufficiently large that L and U will usually round
17902 to the same internal floating value, but if not will round to adjacent values.
17903 </small>
17905 <h5><a name="7.24.4.1.2" href="#7.24.4.1.2">7.24.4.1.2 The wcstol, wcstoll, wcstoul, and wcstoull functions</a></h5>
17908 <pre>
17910 long int wcstol(
17911 const wchar_t * restrict nptr,
17912 wchar_t ** restrict endptr,
17913 int base);
17914 long long int wcstoll(
17915 const wchar_t * restrict nptr,
17916 wchar_t ** restrict endptr,
17917 int base);
17918 unsigned long int wcstoul(
17919 const wchar_t * restrict nptr,
17920 wchar_t ** restrict endptr,
17921 int base);
17922 unsigned long long int wcstoull(
17923 const wchar_t * restrict nptr,
17924 wchar_t ** restrict endptr,
17925 int base);</pre>
17928 The wcstol, wcstoll, wcstoul, and wcstoull functions convert the initial
17929 portion of the wide string pointed to by nptr to long int, long long int,
17930 unsigned long int, and unsigned long long int representation,
17931 respectively. First, they decompose the input string into three parts: an initial, possibly
17932 empty, sequence of white-space wide characters (as specified by the iswspace
17933 function), a subject sequence resembling an integer represented in some radix determined
17934 by the value of base, and a final wide string of one or more unrecognized wide
17935 characters, including the terminating null wide character of the input wide string. Then,
17936 they attempt to convert the subject sequence to an integer, and return the result.
17938 If the value of base is zero, the expected form of the subject sequence is that of an
17939 integer constant as described for the corresponding single-byte characters in <a href="#6.4.4.1">6.4.4.1</a>,
17940 optionally preceded by a plus or minus sign, but not including an integer suffix. If the
17942 is a sequence of letters and digits representing an integer with the radix specified by
17943 base, optionally preceded by a plus or minus sign, but not including an integer suffix.
17945 letters and digits whose ascribed values are less than that of base are permitted. If the
17947 of letters and digits, following the sign if present.
17948 <!--page 388 -->
17950 The subject sequence is defined as the longest initial subsequence of the input wide
17951 string, starting with the first non-white-space wide character, that is of the expected form.
17952 The subject sequence contains no wide characters if the input wide string is empty or
17953 consists entirely of white space, or if the first non-white-space wide character is other
17954 than a sign or a permissible letter or digit.
17956 If the subject sequence has the expected form and the value of base is zero, the sequence
17957 of wide characters starting with the first digit is interpreted as an integer constant
17958 according to the rules of <a href="#6.4.4.1">6.4.4.1</a>. If the subject sequence has the expected form and the
17960 letter its value as given above. If the subject sequence begins with a minus sign, the value
17961 resulting from the conversion is negated (in the return type). A pointer to the final wide
17962 string is stored in the object pointed to by endptr, provided that endptr is not a null
17963 pointer.
17965 In other than the "C" locale, additional locale-specific subject sequence forms may be
17966 accepted.
17968 If the subject sequence is empty or does not have the expected form, no conversion is
17969 performed; the value of nptr is stored in the object pointed to by endptr, provided
17970 that endptr is not a null pointer.
17973 The wcstol, wcstoll, wcstoul, and wcstoull functions return the converted
17974 value, if any. If no conversion could be performed, zero is returned. If the correct value
17975 is outside the range of representable values, LONG_MIN, LONG_MAX, LLONG_MIN,
17976 LLONG_MAX, ULONG_MAX, or ULLONG_MAX is returned (according to the return type
17977 sign of the value, if any), and the value of the macro ERANGE is stored in errno.
17984 <pre>
17986 wchar_t *wcscpy(wchar_t * restrict s1,
17987 const wchar_t * restrict s2);</pre>
17990 The wcscpy function copies the wide string pointed to by s2 (including the terminating
17991 null wide character) into the array pointed to by s1.
17994 The wcscpy function returns the value of s1.
17995 <!--page 389 -->
18000 <pre>
18002 wchar_t *wcsncpy(wchar_t * restrict s1,
18003 const wchar_t * restrict s2,
18004 size_t n);</pre>
18007 The wcsncpy function copies not more than n wide characters (those that follow a null
18008 wide character are not copied) from the array pointed to by s2 to the array pointed to by
18011 If the array pointed to by s2 is a wide string that is shorter than n wide characters, null
18012 wide characters are appended to the copy in the array pointed to by s1, until n wide
18013 characters in all have been written.
18016 The wcsncpy function returns the value of s1.
18019 <p><small><a name="note297" href="#note297">297)</a> Thus, if there is no null wide character in the first n wide characters of the array pointed to by s2, the
18020 result will not be null-terminated.
18021 </small>
18026 <pre>
18028 wchar_t *wmemcpy(wchar_t * restrict s1,
18029 const wchar_t * restrict s2,
18030 size_t n);</pre>
18033 The wmemcpy function copies n wide characters from the object pointed to by s2 to the
18034 object pointed to by s1.
18037 The wmemcpy function returns the value of s1.
18042 <!--page 390 -->
18047 <pre>
18049 wchar_t *wmemmove(wchar_t *s1, const wchar_t *s2,
18050 size_t n);</pre>
18053 The wmemmove function copies n wide characters from the object pointed to by s2 to
18054 the object pointed to by s1. Copying takes place as if the n wide characters from the
18055 object pointed to by s2 are first copied into a temporary array of n wide characters that
18056 does not overlap the objects pointed to by s1 or s2, and then the n wide characters from
18057 the temporary array are copied into the object pointed to by s1.
18060 The wmemmove function returns the value of s1.
18067 <pre>
18069 wchar_t *wcscat(wchar_t * restrict s1,
18070 const wchar_t * restrict s2);</pre>
18073 The wcscat function appends a copy of the wide string pointed to by s2 (including the
18074 terminating null wide character) to the end of the wide string pointed to by s1. The initial
18075 wide character of s2 overwrites the null wide character at the end of s1.
18078 The wcscat function returns the value of s1.
18083 <pre>
18085 wchar_t *wcsncat(wchar_t * restrict s1,
18086 const wchar_t * restrict s2,
18087 size_t n);</pre>
18090 The wcsncat function appends not more than n wide characters (a null wide character
18091 and those that follow it are not appended) from the array pointed to by s2 to the end of
18092 <!--page 391 -->
18093 the wide string pointed to by s1. The initial wide character of s2 overwrites the null
18094 wide character at the end of s1. A terminating null wide character is always appended to
18098 The wcsncat function returns the value of s1.
18101 <p><small><a name="note298" href="#note298">298)</a> Thus, the maximum number of wide characters that can end up in the array pointed to by s1 is
18102 wcslen(s1)+n+1.
18103 </small>
18107 Unless explicitly stated otherwise, the functions described in this subclause order two
18108 wide characters the same way as two integers of the underlying integer type designated
18109 by wchar_t.
18114 <pre>
18116 int wcscmp(const wchar_t *s1, const wchar_t *s2);</pre>
18119 The wcscmp function compares the wide string pointed to by s1 to the wide string
18120 pointed to by s2.
18123 The wcscmp function returns an integer greater than, equal to, or less than zero,
18124 accordingly as the wide string pointed to by s1 is greater than, equal to, or less than the
18125 wide string pointed to by s2.
18130 <pre>
18132 int wcscoll(const wchar_t *s1, const wchar_t *s2);</pre>
18135 The wcscoll function compares the wide string pointed to by s1 to the wide string
18136 pointed to by s2, both interpreted as appropriate to the LC_COLLATE category of the
18137 current locale.
18140 The wcscoll function returns an integer greater than, equal to, or less than zero,
18141 accordingly as the wide string pointed to by s1 is greater than, equal to, or less than the
18144 <!--page 392 -->
18145 wide string pointed to by s2 when both are interpreted as appropriate to the current
18146 locale.
18151 <pre>
18153 int wcsncmp(const wchar_t *s1, const wchar_t *s2,
18154 size_t n);</pre>
18157 The wcsncmp function compares not more than n wide characters (those that follow a
18158 null wide character are not compared) from the array pointed to by s1 to the array
18159 pointed to by s2.
18162 The wcsncmp function returns an integer greater than, equal to, or less than zero,
18163 accordingly as the possibly null-terminated array pointed to by s1 is greater than, equal
18164 to, or less than the possibly null-terminated array pointed to by s2.
18169 <pre>
18171 size_t wcsxfrm(wchar_t * restrict s1,
18172 const wchar_t * restrict s2,
18173 size_t n);</pre>
18176 The wcsxfrm function transforms the wide string pointed to by s2 and places the
18177 resulting wide string into the array pointed to by s1. The transformation is such that if
18178 the wcscmp function is applied to two transformed wide strings, it returns a value greater
18179 than, equal to, or less than zero, corresponding to the result of the wcscoll function
18180 applied to the same two original wide strings. No more than n wide characters are placed
18181 into the resulting array pointed to by s1, including the terminating null wide character. If
18182 n is zero, s1 is permitted to be a null pointer.
18185 The wcsxfrm function returns the length of the transformed wide string (not including
18186 the terminating null wide character). If the value returned is n or greater, the contents of
18187 the array pointed to by s1 are indeterminate.
18189 EXAMPLE The value of the following expression is the length of the array needed to hold the
18190 transformation of the wide string pointed to by s:
18191 <!--page 393 -->
18192 <pre>
18199 <pre>
18201 int wmemcmp(const wchar_t *s1, const wchar_t *s2,
18202 size_t n);</pre>
18205 The wmemcmp function compares the first n wide characters of the object pointed to by
18206 s1 to the first n wide characters of the object pointed to by s2.
18209 The wmemcmp function returns an integer greater than, equal to, or less than zero,
18210 accordingly as the object pointed to by s1 is greater than, equal to, or less than the object
18211 pointed to by s2.
18218 <pre>
18220 wchar_t *wcschr(const wchar_t *s, wchar_t c);</pre>
18223 The wcschr function locates the first occurrence of c in the wide string pointed to by s.
18224 The terminating null wide character is considered to be part of the wide string.
18227 The wcschr function returns a pointer to the located wide character, or a null pointer if
18228 the wide character does not occur in the wide string.
18233 <pre>
18235 size_t wcscspn(const wchar_t *s1, const wchar_t *s2);</pre>
18238 The wcscspn function computes the length of the maximum initial segment of the wide
18239 string pointed to by s1 which consists entirely of wide characters not from the wide
18240 string pointed to by s2.
18241 <!--page 394 -->
18244 The wcscspn function returns the length of the segment.
18249 <pre>
18251 wchar_t *wcspbrk(const wchar_t *s1, const wchar_t *s2);</pre>
18254 The wcspbrk function locates the first occurrence in the wide string pointed to by s1 of
18255 any wide character from the wide string pointed to by s2.
18258 The wcspbrk function returns a pointer to the wide character in s1, or a null pointer if
18259 no wide character from s2 occurs in s1.
18264 <pre>
18266 wchar_t *wcsrchr(const wchar_t *s, wchar_t c);</pre>
18269 The wcsrchr function locates the last occurrence of c in the wide string pointed to by
18270 s. The terminating null wide character is considered to be part of the wide string.
18273 The wcsrchr function returns a pointer to the wide character, or a null pointer if c does
18274 not occur in the wide string.
18279 <pre>
18281 size_t wcsspn(const wchar_t *s1, const wchar_t *s2);</pre>
18284 The wcsspn function computes the length of the maximum initial segment of the wide
18285 string pointed to by s1 which consists entirely of wide characters from the wide string
18286 pointed to by s2.
18289 The wcsspn function returns the length of the segment.
18290 <!--page 395 -->
18295 <pre>
18297 wchar_t *wcsstr(const wchar_t *s1, const wchar_t *s2);</pre>
18300 The wcsstr function locates the first occurrence in the wide string pointed to by s1 of
18301 the sequence of wide characters (excluding the terminating null wide character) in the
18302 wide string pointed to by s2.
18305 The wcsstr function returns a pointer to the located wide string, or a null pointer if the
18306 wide string is not found. If s2 points to a wide string with zero length, the function
18307 returns s1.
18312 <pre>
18314 wchar_t *wcstok(wchar_t * restrict s1,
18315 const wchar_t * restrict s2,
18316 wchar_t ** restrict ptr);</pre>
18319 A sequence of calls to the wcstok function breaks the wide string pointed to by s1 into
18320 a sequence of tokens, each of which is delimited by a wide character from the wide string
18321 pointed to by s2. The third argument points to a caller-provided wchar_t pointer into
18322 which the wcstok function stores information necessary for it to continue scanning the
18323 same wide string.
18325 The first call in a sequence has a non-null first argument and stores an initial value in the
18326 object pointed to by ptr. Subsequent calls in the sequence have a null first argument and
18327 the object pointed to by ptr is required to have the value stored by the previous call in
18328 the sequence, which is then updated. The separator wide string pointed to by s2 may be
18329 different from call to call.
18331 The first call in the sequence searches the wide string pointed to by s1 for the first wide
18332 character that is not contained in the current separator wide string pointed to by s2. If no
18333 such wide character is found, then there are no tokens in the wide string pointed to by s1
18334 and the wcstok function returns a null pointer. If such a wide character is found, it is
18335 the start of the first token.
18337 The wcstok function then searches from there for a wide character that is contained in
18338 the current separator wide string. If no such wide character is found, the current token
18339 <!--page 396 -->
18340 extends to the end of the wide string pointed to by s1, and subsequent searches in the
18341 same wide string for a token return a null pointer. If such a wide character is found, it is
18342 overwritten by a null wide character, which terminates the current token.
18344 In all cases, the wcstok function stores sufficient information in the pointer pointed to
18345 by ptr so that subsequent calls, with a null pointer for s1 and the unmodified pointer
18346 value for ptr, shall start searching just past the element overwritten by a null wide
18347 character (if any).
18350 The wcstok function returns a pointer to the first wide character of a token, or a null
18351 pointer if there is no token.
18353 EXAMPLE
18354 <pre>
18356 static wchar_t str1[] = L"?a???b,,,#c";
18357 static wchar_t str2[] = L"\t \t";
18358 wchar_t *t, *ptr1, *ptr2;
18369 <pre>
18371 wchar_t *wmemchr(const wchar_t *s, wchar_t c,
18372 size_t n);</pre>
18375 The wmemchr function locates the first occurrence of c in the initial n wide characters of
18376 the object pointed to by s.
18379 The wmemchr function returns a pointer to the located wide character, or a null pointer if
18380 the wide character does not occur in the object.
18381 <!--page 397 -->
18388 <pre>
18390 size_t wcslen(const wchar_t *s);</pre>
18393 The wcslen function computes the length of the wide string pointed to by s.
18396 The wcslen function returns the number of wide characters that precede the terminating
18397 null wide character.
18402 <pre>
18404 wchar_t *wmemset(wchar_t *s, wchar_t c, size_t n);</pre>
18407 The wmemset function copies the value of c into each of the first n wide characters of
18408 the object pointed to by s.
18411 The wmemset function returns the value of s.
18418 <pre>
18421 size_t wcsftime(wchar_t * restrict s,
18422 size_t maxsize,
18423 const wchar_t * restrict format,
18424 const struct tm * restrict timeptr);</pre>
18427 The wcsftime function is equivalent to the strftime function, except that:
18428 <ul>
18429 <li> The argument s points to the initial element of an array of wide characters into which
18430 the generated output is to be placed.
18431 <!--page 398 -->
18432 <li> The argument maxsize indicates the limiting number of wide characters.
18433 <li> The argument format is a wide string and the conversion specifiers are replaced by
18434 corresponding sequences of wide characters.
18435 <li> The return value indicates the number of wide characters.
18436 </ul>
18439 If the total number of resulting wide characters including the terminating null wide
18440 character is not more than maxsize, the wcsftime function returns the number of
18441 wide characters placed into the array pointed to by s not including the terminating null
18442 wide character. Otherwise, zero is returned and the contents of the array are
18443 indeterminate.
18445 <h4><a name="7.24.6" href="#7.24.6">7.24.6 Extended multibyte/wide character conversion utilities</a></h4>
18447 The header <a href="#7.24"><wchar.h></a> declares an extended set of functions useful for conversion
18448 between multibyte characters and wide characters.
18450 Most of the following functions -- those that are listed as ''restartable'', <a href="#7.24.6.3">7.24.6.3</a> and
18451 <a href="#7.24.6.4">7.24.6.4</a> -- take as a last argument a pointer to an object of type mbstate_t that is used
18452 to describe the current conversion state from a particular multibyte character sequence to
18453 a wide character sequence (or the reverse) under the rules of a particular setting for the
18454 LC_CTYPE category of the current locale.
18456 The initial conversion state corresponds, for a conversion in either direction, to the
18457 beginning of a new multibyte character in the initial shift state. A zero-valued
18458 mbstate_t object is (at least) one way to describe an initial conversion state. A zero-
18459 valued mbstate_t object can be used to initiate conversion involving any multibyte
18460 character sequence, in any LC_CTYPE category setting. If an mbstate_t object has
18461 been altered by any of the functions described in this subclause, and is then used with a
18462 different multibyte character sequence, or in the other conversion direction, or with a
18463 different LC_CTYPE category setting than on earlier function calls, the behavior is
18466 On entry, each function takes the described conversion state (either internal or pointed to
18467 by an argument) as current. The conversion state described by the pointed-to object is
18468 altered as needed to track the shift state, and the position within a multibyte character, for
18469 the associated multibyte character sequence.
18474 <!--page 399 -->
18477 <p><small><a name="note299" href="#note299">299)</a> Thus, a particular mbstate_t object can be used, for example, with both the mbrtowc and
18478 mbsrtowcs functions as long as they are used to step sequentially through the same multibyte
18479 character string.
18480 </small>
18482 <h5><a name="7.24.6.1" href="#7.24.6.1">7.24.6.1 Single-byte/wide character conversion functions</a></h5>
18487 <pre>
18490 wint_t btowc(int c);</pre>
18493 The btowc function determines whether c constitutes a valid single-byte character in the
18494 initial shift state.
18497 The btowc function returns WEOF if c has the value EOF or if (unsigned char)c
18498 does not constitute a valid single-byte character in the initial shift state. Otherwise, it
18499 returns the wide character representation of that character.
18504 <pre>
18507 int wctob(wint_t c);</pre>
18510 The wctob function determines whether c corresponds to a member of the extended
18511 character set whose multibyte character representation is a single byte when in the initial
18512 shift state.
18515 The wctob function returns EOF if c does not correspond to a multibyte character with
18516 length one in the initial shift state. Otherwise, it returns the single-byte representation of
18517 that character as an unsigned char converted to an int.
18524 <pre>
18526 int mbsinit(const mbstate_t *ps);</pre>
18529 If ps is not a null pointer, the mbsinit function determines whether the pointed-to
18530 mbstate_t object describes an initial conversion state.
18531 <!--page 400 -->
18534 The mbsinit function returns nonzero if ps is a null pointer or if the pointed-to object
18535 describes an initial conversion state; otherwise, it returns zero.
18537 <h5><a name="7.24.6.3" href="#7.24.6.3">7.24.6.3 Restartable multibyte/wide character conversion functions</a></h5>
18539 These functions differ from the corresponding multibyte character functions of <a href="#7.20.7">7.20.7</a>
18540 (mblen, mbtowc, and wctomb) in that they have an extra parameter, ps, of type
18541 pointer to mbstate_t that points to an object that can completely describe the current
18542 conversion state of the associated multibyte character sequence. If ps is a null pointer,
18543 each function uses its own internal mbstate_t object instead, which is initialized at
18544 program startup to the initial conversion state. The implementation behaves as if no
18545 library function calls these functions with a null pointer for ps.
18547 Also unlike their corresponding functions, the return value does not represent whether the
18548 encoding is state-dependent.
18553 <pre>
18555 size_t mbrlen(const char * restrict s,
18556 size_t n,
18557 mbstate_t * restrict ps);</pre>
18560 The mbrlen function is equivalent to the call:
18561 <pre>
18563 where internal is the mbstate_t object for the mbrlen function, except that the
18564 expression designated by ps is evaluated only once.
18567 The mbrlen function returns a value between zero and n, inclusive, (size_t)(-2),
18568 or (size_t)(-1).
18570 <!--page 401 -->
18575 <pre>
18577 size_t mbrtowc(wchar_t * restrict pwc,
18578 const char * restrict s,
18579 size_t n,
18580 mbstate_t * restrict ps);</pre>
18583 If s is a null pointer, the mbrtowc function is equivalent to the call:
18584 <pre>
18586 In this case, the values of the parameters pwc and n are ignored.
18588 If s is not a null pointer, the mbrtowc function inspects at most n bytes beginning with
18589 the byte pointed to by s to determine the number of bytes needed to complete the next
18590 multibyte character (including any shift sequences). If the function determines that the
18591 next multibyte character is complete and valid, it determines the value of the
18592 corresponding wide character and then, if pwc is not a null pointer, stores that value in
18593 the object pointed to by pwc. If the corresponding wide character is the null wide
18594 character, the resulting state described is the initial conversion state.
18597 The mbrtowc function returns the first of the following that applies (given the current
18598 conversion state):
18599 0 if the next n or fewer bytes complete the multibyte character that
18600 <pre>
18601 corresponds to the null wide character (which is the value stored).</pre>
18602 between 1 and n inclusive if the next n or fewer bytes complete a valid multibyte
18603 <pre>
18604 character (which is the value stored); the value returned is the number
18605 of bytes that complete the multibyte character.</pre>
18606 (size_t)(-2) if the next n bytes contribute to an incomplete (but potentially valid)
18607 <pre>
18608 multibyte character, and all n bytes have been processed (no value is
18610 (size_t)(-1) if an encoding error occurs, in which case the next n or fewer bytes
18611 <pre>
18612 do not contribute to a complete and valid multibyte character (no
18613 value is stored); the value of the macro EILSEQ is stored in errno,
18614 and the conversion state is unspecified.</pre>
18616 <!--page 402 -->
18619 <p><small><a name="note300" href="#note300">300)</a> When n has at least the value of the MB_CUR_MAX macro, this case can only occur if s points at a
18620 sequence of redundant shift sequences (for implementations with state-dependent encodings).
18621 </small>
18626 <pre>
18628 size_t wcrtomb(char * restrict s,
18629 wchar_t wc,
18630 mbstate_t * restrict ps);</pre>
18633 If s is a null pointer, the wcrtomb function is equivalent to the call
18634 <pre>
18636 where buf is an internal buffer.
18638 If s is not a null pointer, the wcrtomb function determines the number of bytes needed
18639 to represent the multibyte character that corresponds to the wide character given by wc
18640 (including any shift sequences), and stores the multibyte character representation in the
18641 array whose first element is pointed to by s. At most MB_CUR_MAX bytes are stored. If
18642 wc is a null wide character, a null byte is stored, preceded by any shift sequence needed
18643 to restore the initial shift state; the resulting state described is the initial conversion state.
18646 The wcrtomb function returns the number of bytes stored in the array object (including
18647 any shift sequences). When wc is not a valid wide character, an encoding error occurs:
18648 the function stores the value of the macro EILSEQ in errno and returns
18649 (size_t)(-1); the conversion state is unspecified.
18651 <h5><a name="7.24.6.4" href="#7.24.6.4">7.24.6.4 Restartable multibyte/wide string conversion functions</a></h5>
18653 These functions differ from the corresponding multibyte string functions of <a href="#7.20.8">7.20.8</a>
18654 (mbstowcs and wcstombs) in that they have an extra parameter, ps, of type pointer to
18655 mbstate_t that points to an object that can completely describe the current conversion
18656 state of the associated multibyte character sequence. If ps is a null pointer, each function
18657 uses its own internal mbstate_t object instead, which is initialized at program startup
18658 to the initial conversion state. The implementation behaves as if no library function calls
18659 these functions with a null pointer for ps.
18661 Also unlike their corresponding functions, the conversion source parameter, src, has a
18662 pointer-to-pointer type. When the function is storing the results of conversions (that is,
18663 when dst is not a null pointer), the pointer object pointed to by this parameter is updated
18664 to reflect the amount of the source processed by that invocation.
18665 <!--page 403 -->
18670 <pre>
18672 size_t mbsrtowcs(wchar_t * restrict dst,
18673 const char ** restrict src,
18674 size_t len,
18675 mbstate_t * restrict ps);</pre>
18678 The mbsrtowcs function converts a sequence of multibyte characters that begins in the
18679 conversion state described by the object pointed to by ps, from the array indirectly
18680 pointed to by src into a sequence of corresponding wide characters. If dst is not a null
18681 pointer, the converted characters are stored into the array pointed to by dst. Conversion
18682 continues up to and including a terminating null character, which is also stored.
18683 Conversion stops earlier in two cases: when a sequence of bytes is encountered that does
18684 not form a valid multibyte character, or (if dst is not a null pointer) when len wide
18685 characters have been stored into the array pointed to by dst.<sup><a href="#note301"><b>301)</b></a></sup> Each conversion takes
18686 place as if by a call to the mbrtowc function.
18688 If dst is not a null pointer, the pointer object pointed to by src is assigned either a null
18689 pointer (if conversion stopped due to reaching a terminating null character) or the address
18690 just past the last multibyte character converted (if any). If conversion stopped due to
18691 reaching a terminating null character and if dst is not a null pointer, the resulting state
18692 described is the initial conversion state.
18695 If the input conversion encounters a sequence of bytes that do not form a valid multibyte
18696 character, an encoding error occurs: the mbsrtowcs function stores the value of the
18697 macro EILSEQ in errno and returns (size_t)(-1); the conversion state is
18698 unspecified. Otherwise, it returns the number of multibyte characters successfully
18699 converted, not including the terminating null character (if any).
18704 <!--page 404 -->
18707 <p><small><a name="note301" href="#note301">301)</a> Thus, the value of len is ignored if dst is a null pointer.
18708 </small>
18713 <pre>
18715 size_t wcsrtombs(char * restrict dst,
18716 const wchar_t ** restrict src,
18717 size_t len,
18718 mbstate_t * restrict ps);</pre>
18721 The wcsrtombs function converts a sequence of wide characters from the array
18722 indirectly pointed to by src into a sequence of corresponding multibyte characters that
18723 begins in the conversion state described by the object pointed to by ps. If dst is not a
18724 null pointer, the converted characters are then stored into the array pointed to by dst.
18725 Conversion continues up to and including a terminating null wide character, which is also
18726 stored. Conversion stops earlier in two cases: when a wide character is reached that does
18727 not correspond to a valid multibyte character, or (if dst is not a null pointer) when the
18728 next multibyte character would exceed the limit of len total bytes to be stored into the
18729 array pointed to by dst. Each conversion takes place as if by a call to the wcrtomb
18732 If dst is not a null pointer, the pointer object pointed to by src is assigned either a null
18733 pointer (if conversion stopped due to reaching a terminating null wide character) or the
18734 address just past the last wide character converted (if any). If conversion stopped due to
18735 reaching a terminating null wide character, the resulting state described is the initial
18736 conversion state.
18739 If conversion stops because a wide character is reached that does not correspond to a
18740 valid multibyte character, an encoding error occurs: the wcsrtombs function stores the
18741 value of the macro EILSEQ in errno and returns (size_t)(-1); the conversion
18742 state is unspecified. Otherwise, it returns the number of bytes in the resulting multibyte
18743 character sequence, not including the terminating null character (if any).
18748 <!--page 405 -->
18751 <p><small><a name="note302" href="#note302">302)</a> If conversion stops because a terminating null wide character has been reached, the bytes stored
18752 include those necessary to reach the initial shift state immediately before the null byte.
18753 </small>
18755 <h3><a name="7.25" href="#7.25">7.25 Wide character classification and mapping utilities <wctype.h></a></h3>
18759 The header <a href="#7.25"><wctype.h></a> declares three data types, one macro, and many functions.<sup><a href="#note303"><b>303)</b></a></sup>
18761 The types declared are
18762 <pre>
18763 wint_t</pre>
18765 <pre>
18766 wctrans_t</pre>
18767 which is a scalar type that can hold values which represent locale-specific character
18768 mappings; and
18769 <pre>
18770 wctype_t</pre>
18771 which is a scalar type that can hold values which represent locale-specific character
18772 classifications.
18776 The functions declared are grouped as follows:
18777 <ul>
18778 <li> Functions that provide wide character classification;
18779 <li> Extensible functions that provide wide character classification;
18780 <li> Functions that provide wide character case mapping;
18781 <li> Extensible functions that provide wide character mapping.
18782 </ul>
18784 For all functions described in this subclause that accept an argument of type wint_t, the
18785 value shall be representable as a wchar_t or shall equal the value of the macro WEOF. If
18786 this argument has any other value, the behavior is undefined.
18788 The behavior of these functions is affected by the LC_CTYPE category of the current
18789 locale.
18794 <!--page 406 -->
18797 <p><small><a name="note303" href="#note303">303)</a> See ''future library directions'' (<a href="#7.26.13">7.26.13</a>).
18798 </small>
18802 The header <a href="#7.25"><wctype.h></a> declares several functions useful for classifying wide
18803 characters.
18805 The term printing wide character refers to a member of a locale-specific set of wide
18806 characters, each of which occupies at least one printing position on a display device. The
18807 term control wide character refers to a member of a locale-specific set of wide characters
18808 that are not printing wide characters.
18810 <h5><a name="7.25.2.1" href="#7.25.2.1">7.25.2.1 Wide character classification functions</a></h5>
18812 The functions in this subclause return nonzero (true) if and only if the value of the
18813 argument wc conforms to that in the description of the function.
18815 Each of the following functions returns true for each wide character that corresponds (as
18816 if by a call to the wctob function) to a single-byte character for which the corresponding
18817 character classification function from <a href="#7.4.1">7.4.1</a> returns true, except that the iswgraph and
18818 iswpunct functions may differ with respect to wide characters other than L' ' that are
18823 <p><small><a name="note304" href="#note304">304)</a> For example, if the expression isalpha(wctob(wc)) evaluates to true, then the call
18824 iswalpha(wc) also returns true. But, if the expression isgraph(wctob(wc)) evaluates to true
18825 (which cannot occur for wc == L' ' of course), then either iswgraph(wc) or iswprint(wc)
18826 && iswspace(wc) is true, but not both.
18827 </small>
18832 <pre>
18834 int iswalnum(wint_t wc);</pre>
18837 The iswalnum function tests for any wide character for which iswalpha or
18838 iswdigit is true.
18843 <pre>
18845 int iswalpha(wint_t wc);</pre>
18848 The iswalpha function tests for any wide character for which iswupper or
18849 iswlower is true, or any wide character that is one of a locale-specific set of alphabetic
18851 <!--page 407 -->
18852 wide characters for which none of iswcntrl, iswdigit, iswpunct, or iswspace
18856 <p><small><a name="note305" href="#note305">305)</a> The functions iswlower and iswupper test true or false separately for each of these additional
18857 wide characters; all four combinations are possible.
18858 </small>
18863 <pre>
18865 int iswblank(wint_t wc);</pre>
18868 The iswblank function tests for any wide character that is a standard blank wide
18869 character or is one of a locale-specific set of wide characters for which iswspace is true
18870 and that is used to separate words within a line of text. The standard blank wide
18871 characters are the following: space (L' '), and horizontal tab (L'\t'). In the "C"
18872 locale, iswblank returns true only for the standard blank characters.
18877 <pre>
18879 int iswcntrl(wint_t wc);</pre>
18882 The iswcntrl function tests for any control wide character.
18887 <pre>
18889 int iswdigit(wint_t wc);</pre>
18892 The iswdigit function tests for any wide character that corresponds to a decimal-digit
18898 <pre>
18900 int iswgraph(wint_t wc);</pre>
18905 <!--page 408 -->
18908 The iswgraph function tests for any wide character for which iswprint is true and
18912 <p><small><a name="note306" href="#note306">306)</a> Note that the behavior of the iswgraph and iswpunct functions may differ from their
18913 corresponding functions in <a href="#7.4.1">7.4.1</a> with respect to printing, white-space, single-byte execution
18914 characters other than ' '.
18915 </small>
18920 <pre>
18922 int iswlower(wint_t wc);</pre>
18925 The iswlower function tests for any wide character that corresponds to a lowercase
18926 letter or is one of a locale-specific set of wide characters for which none of iswcntrl,
18927 iswdigit, iswpunct, or iswspace is true.
18932 <pre>
18934 int iswprint(wint_t wc);</pre>
18937 The iswprint function tests for any printing wide character.
18942 <pre>
18944 int iswpunct(wint_t wc);</pre>
18947 The iswpunct function tests for any printing wide character that is one of a locale-
18948 specific set of punctuation wide characters for which neither iswspace nor iswalnum
18949 is true.306)
18954 <pre>
18956 int iswspace(wint_t wc);</pre>
18960 <!--page 409 -->
18963 The iswspace function tests for any wide character that corresponds to a locale-specific
18964 set of white-space wide characters for which none of iswalnum, iswgraph, or
18965 iswpunct is true.
18970 <pre>
18972 int iswupper(wint_t wc);</pre>
18975 The iswupper function tests for any wide character that corresponds to an uppercase
18976 letter or is one of a locale-specific set of wide characters for which none of iswcntrl,
18977 iswdigit, iswpunct, or iswspace is true.
18982 <pre>
18984 int iswxdigit(wint_t wc);</pre>
18987 The iswxdigit function tests for any wide character that corresponds to a
18990 <h5><a name="7.25.2.2" href="#7.25.2.2">7.25.2.2 Extensible wide character classification functions</a></h5>
18992 The functions wctype and iswctype provide extensible wide character classification
18993 as well as testing equivalent to that performed by the functions described in the previous
18999 <pre>
19001 int iswctype(wint_t wc, wctype_t desc);</pre>
19004 The iswctype function determines whether the wide character wc has the property
19005 described by desc. The current setting of the LC_CTYPE category shall be the same as
19006 during the call to wctype that returned the value desc.
19008 Each of the following expressions has a truth-value equivalent to the call to the wide
19009 character classification function (<a href="#7.25.2.1">7.25.2.1</a>) in the comment that follows the expression:
19010 <!--page 410 -->
19011 <pre>
19012 iswctype(wc, wctype("alnum")) // iswalnum(wc)
19013 iswctype(wc, wctype("alpha")) // iswalpha(wc)
19014 iswctype(wc, wctype("blank")) // iswblank(wc)
19015 iswctype(wc, wctype("cntrl")) // iswcntrl(wc)
19016 iswctype(wc, wctype("digit")) // iswdigit(wc)
19017 iswctype(wc, wctype("graph")) // iswgraph(wc)
19018 iswctype(wc, wctype("lower")) // iswlower(wc)
19019 iswctype(wc, wctype("print")) // iswprint(wc)
19020 iswctype(wc, wctype("punct")) // iswpunct(wc)
19021 iswctype(wc, wctype("space")) // iswspace(wc)
19022 iswctype(wc, wctype("upper")) // iswupper(wc)
19026 The iswctype function returns nonzero (true) if and only if the value of the wide
19027 character wc has the property described by desc.
19033 <pre>
19035 wctype_t wctype(const char *property);</pre>
19038 The wctype function constructs a value with type wctype_t that describes a class of
19039 wide characters identified by the string argument property.
19041 The strings listed in the description of the iswctype function shall be valid in all
19042 locales as property arguments to the wctype function.
19045 If property identifies a valid class of wide characters according to the LC_CTYPE
19046 category of the current locale, the wctype function returns a nonzero value that is valid
19047 as the second argument to the iswctype function; otherwise, it returns zero. *
19048 <!--page 411 -->
19052 The header <a href="#7.25"><wctype.h></a> declares several functions useful for mapping wide characters.
19054 <h5><a name="7.25.3.1" href="#7.25.3.1">7.25.3.1 Wide character case mapping functions</a></h5>
19059 <pre>
19061 wint_t towlower(wint_t wc);</pre>
19064 The towlower function converts an uppercase letter to a corresponding lowercase letter.
19067 If the argument is a wide character for which iswupper is true and there are one or
19068 more corresponding wide characters, as specified by the current locale, for which
19069 iswlower is true, the towlower function returns one of the corresponding wide
19070 characters (always the same one for any given locale); otherwise, the argument is
19071 returned unchanged.
19076 <pre>
19078 wint_t towupper(wint_t wc);</pre>
19081 The towupper function converts a lowercase letter to a corresponding uppercase letter.
19084 If the argument is a wide character for which iswlower is true and there are one or
19085 more corresponding wide characters, as specified by the current locale, for which
19086 iswupper is true, the towupper function returns one of the corresponding wide
19087 characters (always the same one for any given locale); otherwise, the argument is
19088 returned unchanged.
19090 <h5><a name="7.25.3.2" href="#7.25.3.2">7.25.3.2 Extensible wide character case mapping functions</a></h5>
19092 The functions wctrans and towctrans provide extensible wide character mapping as
19093 well as case mapping equivalent to that performed by the functions described in the
19095 <!--page 412 -->
19100 <pre>
19102 wint_t towctrans(wint_t wc, wctrans_t desc);</pre>
19105 The towctrans function maps the wide character wc using the mapping described by
19106 desc. The current setting of the LC_CTYPE category shall be the same as during the call
19107 to wctrans that returned the value desc.
19109 Each of the following expressions behaves the same as the call to the wide character case
19110 mapping function (<a href="#7.25.3.1">7.25.3.1</a>) in the comment that follows the expression:
19111 <pre>
19112 towctrans(wc, wctrans("tolower")) // towlower(wc)
19116 The towctrans function returns the mapped value of wc using the mapping described
19117 by desc.
19122 <pre>
19124 wctrans_t wctrans(const char *property);</pre>
19127 The wctrans function constructs a value with type wctrans_t that describes a
19128 mapping between wide characters identified by the string argument property.
19130 The strings listed in the description of the towctrans function shall be valid in all
19131 locales as property arguments to the wctrans function.
19134 If property identifies a valid mapping of wide characters according to the LC_CTYPE
19135 category of the current locale, the wctrans function returns a nonzero value that is valid
19136 as the second argument to the towctrans function; otherwise, it returns zero.
19137 <!--page 413 -->
19141 The following names are grouped under individual headers for convenience. All external
19142 names described below are reserved no matter what headers are included by the program.
19146 The function names
19147 <pre>
19148 cerf cexpm1 clog2
19149 cerfc clog10 clgamma
19150 cexp2 clog1p ctgamma</pre>
19151 and the same names suffixed with f or l may be added to the declarations in the
19156 Function names that begin with either is or to, and a lowercase letter may be added to
19161 Macros that begin with E and a digit or E and an uppercase letter may be added to the
19164 <h4><a name="7.26.4" href="#7.26.4">7.26.4 Format conversion of integer types <inttypes.h></a></h4>
19166 Macro names beginning with PRI or SCN followed by any lowercase letter or X may be
19171 Macros that begin with LC_ and an uppercase letter may be added to the definitions in
19176 Macros that begin with either SIG and an uppercase letter or SIG_ and an uppercase
19181 The ability to undefine and perhaps then redefine the macros bool, true, and false is
19182 an obsolescent feature.
19186 Typedef names beginning with int or uint and ending with _t may be added to the
19187 types defined in the <a href="#7.18"><stdint.h></a> header. Macro names beginning with INT or UINT
19188 and ending with _MAX, _MIN, or _C may be added to the macros defined in the
19190 <!--page 414 -->
19194 Lowercase letters may be added to the conversion specifiers and length modifiers in
19195 fprintf and fscanf. Other characters may be used in extensions.
19197 The gets function is obsolescent, and is deprecated.
19199 The use of ungetc on a binary stream where the file position indicator is zero prior to
19200 the call is an obsolescent feature.
19204 Function names that begin with str and a lowercase letter may be added to the
19209 Function names that begin with str, mem, or wcs and a lowercase letter may be added
19212 <h4><a name="7.26.12" href="#7.26.12">7.26.12 Extended multibyte and wide character utilities <wchar.h></a></h4>
19214 Function names that begin with wcs and a lowercase letter may be added to the
19217 Lowercase letters may be added to the conversion specifiers and length modifiers in
19218 fwprintf and fwscanf. Other characters may be used in extensions.
19220 <h4><a name="7.26.13" href="#7.26.13">7.26.13 Wide character classification and mapping utilities</a></h4>
19223 Function names that begin with is or to and a lowercase letter may be added to the
19225 <!--page 415 -->
19229 <pre>
19230 (informative)
19231 Language syntax summary</pre>
19239 <pre>
19240 keyword
19241 identifier
19242 constant
19243 string-literal
19244 punctuator</pre>
19246 <pre>
19247 header-name
19248 identifier
19249 pp-number
19250 character-constant
19251 string-literal
19252 punctuator
19253 each non-white-space character that cannot be one of the above</pre>
19257 <!--page 416 -->
19258 <pre>
19259 auto enum restrict unsigned
19260 break extern return void
19261 case float short volatile
19262 char for signed while
19263 const goto sizeof _Bool
19264 continue if static _Complex
19265 default inline struct _Imaginary
19266 do int switch
19267 double long typedef
19268 else register union</pre>
19272 <pre>
19273 identifier-nondigit
19274 identifier identifier-nondigit
19275 identifier digit</pre>
19277 <pre>
19278 nondigit
19279 universal-character-name
19280 other implementation-defined characters</pre>
19282 <pre>
19283 _ a b c d e f g h i j k l m
19284 n o p q r s t u v w x y z
19285 A B C D E F G H I J K L M
19286 N O P Q R S T U V W X Y Z</pre>
19288 <pre>
19293 <pre>
19294 \u hex-quad
19295 \U hex-quad hex-quad</pre>
19297 <pre>
19298 hexadecimal-digit hexadecimal-digit
19299 hexadecimal-digit hexadecimal-digit</pre>
19303 <pre>
19304 integer-constant
19305 floating-constant
19306 enumeration-constant
19307 character-constant</pre>
19309 <pre>
19310 decimal-constant integer-suffixopt
19311 octal-constant integer-suffixopt
19312 hexadecimal-constant integer-suffixopt</pre>
19314 <!--page 417 -->
19315 <pre>
19316 nonzero-digit
19317 decimal-constant digit</pre>
19319 <pre>
19320 0
19321 octal-constant octal-digit</pre>
19323 <pre>
19324 hexadecimal-prefix hexadecimal-digit
19325 hexadecimal-constant hexadecimal-digit</pre>
19327 <pre>
19330 <pre>
19333 <pre>
19336 <pre>
19337 0 1 2 3 4 5 6 7 8 9
19338 a b c d e f
19339 A B C D E F</pre>
19341 <pre>
19342 unsigned-suffix long-suffixopt
19343 unsigned-suffix long-long-suffix
19344 long-suffix unsigned-suffixopt
19345 long-long-suffix unsigned-suffixopt</pre>
19347 <pre>
19348 u U</pre>
19350 <pre>
19351 l L</pre>
19353 <pre>
19354 ll LL</pre>
19356 <pre>
19357 decimal-floating-constant
19358 hexadecimal-floating-constant</pre>
19360 <!--page 418 -->
19361 <pre>
19362 fractional-constant exponent-partopt floating-suffixopt
19363 digit-sequence exponent-part floating-suffixopt</pre>
19365 <pre>
19366 hexadecimal-prefix hexadecimal-fractional-constant
19367 binary-exponent-part floating-suffixopt
19368 hexadecimal-prefix hexadecimal-digit-sequence
19369 binary-exponent-part floating-suffixopt</pre>
19371 <pre>
19372 digit-sequenceopt . digit-sequence
19373 digit-sequence .</pre>
19375 <pre>
19376 e signopt digit-sequence
19377 E signopt digit-sequence</pre>
19379 <pre>
19380 + -</pre>
19382 <pre>
19383 digit
19384 digit-sequence digit</pre>
19386 <pre>
19387 hexadecimal-digit-sequenceopt .
19388 hexadecimal-digit-sequence
19389 hexadecimal-digit-sequence .</pre>
19391 <pre>
19392 p signopt digit-sequence
19393 P signopt digit-sequence</pre>
19395 <pre>
19396 hexadecimal-digit
19397 hexadecimal-digit-sequence hexadecimal-digit</pre>
19399 <pre>
19400 f l F L</pre>
19402 <pre>
19403 identifier</pre>
19405 <!--page 419 -->
19406 <pre>
19407 ' c-char-sequence '
19408 L' c-char-sequence '</pre>
19410 <pre>
19411 c-char
19412 c-char-sequence c-char</pre>
19414 <pre>
19415 any member of the source character set except
19416 the single-quote ', backslash \, or new-line character
19417 escape-sequence</pre>
19419 <pre>
19420 simple-escape-sequence
19421 octal-escape-sequence
19422 hexadecimal-escape-sequence
19423 universal-character-name</pre>
19425 <pre>
19426 \' \" \? \\
19427 \a \b \f \n \r \t \v</pre>
19429 <pre>
19430 \ octal-digit
19431 \ octal-digit octal-digit
19432 \ octal-digit octal-digit octal-digit</pre>
19434 <pre>
19435 \x hexadecimal-digit
19436 hexadecimal-escape-sequence hexadecimal-digit</pre>
19440 <pre>
19444 <pre>
19445 s-char
19446 s-char-sequence s-char</pre>
19448 <!--page 420 -->
19449 <pre>
19450 any member of the source character set except
19451 the double-quote ", backslash \, or new-line character
19452 escape-sequence</pre>
19456 <pre>
19457 [ ] ( ) { } . ->
19458 ++ -- & * + - ~ !
19460 ? : ; ...
19462 , # ##
19467 <pre>
19471 <pre>
19472 h-char
19473 h-char-sequence h-char</pre>
19475 <pre>
19476 any member of the source character set except
19479 <pre>
19480 q-char
19481 q-char-sequence q-char</pre>
19483 <pre>
19484 any member of the source character set except
19485 the new-line character and "</pre>
19489 <!--page 421 -->
19490 <pre>
19491 digit
19492 . digit
19493 pp-number digit
19494 pp-number identifier-nondigit
19495 pp-number e sign
19496 pp-number E sign
19497 pp-number p sign
19498 pp-number P sign
19499 pp-number .</pre>
19505 <pre>
19506 identifier
19507 constant
19508 string-literal
19509 ( expression )</pre>
19511 <pre>
19512 primary-expression
19513 postfix-expression [ expression ]
19514 postfix-expression ( argument-expression-listopt )
19515 postfix-expression . identifier
19516 postfix-expression -> identifier
19517 postfix-expression ++
19518 postfix-expression --
19519 ( type-name ) { initializer-list }
19520 ( type-name ) { initializer-list , }</pre>
19522 <pre>
19523 assignment-expression
19524 argument-expression-list , assignment-expression</pre>
19526 <pre>
19527 postfix-expression
19528 ++ unary-expression
19529 -- unary-expression
19530 unary-operator cast-expression
19531 sizeof unary-expression
19532 sizeof ( type-name )</pre>
19534 <pre>
19535 & * + - ~ !</pre>
19537 <pre>
19538 unary-expression
19539 ( type-name ) cast-expression</pre>
19541 <!--page 422 -->
19542 <pre>
19543 cast-expression
19544 multiplicative-expression * cast-expression
19545 multiplicative-expression / cast-expression
19546 multiplicative-expression % cast-expression</pre>
19548 <pre>
19549 multiplicative-expression
19550 additive-expression + multiplicative-expression
19551 additive-expression - multiplicative-expression</pre>
19553 <pre>
19554 additive-expression
19555 shift-expression << additive-expression
19556 shift-expression >> additive-expression</pre>
19558 <pre>
19559 shift-expression
19560 relational-expression < shift-expression
19561 relational-expression > shift-expression
19562 relational-expression <= shift-expression
19563 relational-expression >= shift-expression</pre>
19565 <pre>
19566 relational-expression
19567 equality-expression == relational-expression
19568 equality-expression != relational-expression</pre>
19570 <pre>
19571 equality-expression
19572 AND-expression & equality-expression</pre>
19574 <pre>
19575 AND-expression
19576 exclusive-OR-expression ^ AND-expression</pre>
19578 <pre>
19579 exclusive-OR-expression
19580 inclusive-OR-expression | exclusive-OR-expression</pre>
19582 <pre>
19583 inclusive-OR-expression
19584 logical-AND-expression && inclusive-OR-expression</pre>
19586 <pre>
19587 logical-AND-expression
19588 logical-OR-expression || logical-AND-expression</pre>
19590 <!--page 423 -->
19591 <pre>
19592 logical-OR-expression
19593 logical-OR-expression ? expression : conditional-expression</pre>
19595 <pre>
19596 conditional-expression
19597 unary-expression assignment-operator assignment-expression</pre>
19599 <pre>
19600 = *= /= %= += -= <<= >>= &= ^= |=</pre>
19602 <pre>
19603 assignment-expression
19604 expression , assignment-expression</pre>
19606 <pre>
19607 conditional-expression</pre>
19611 <pre>
19612 declaration-specifiers init-declarator-listopt ;</pre>
19614 <pre>
19615 storage-class-specifier declaration-specifiersopt
19616 type-specifier declaration-specifiersopt
19617 type-qualifier declaration-specifiersopt
19618 function-specifier declaration-specifiersopt</pre>
19620 <pre>
19621 init-declarator
19622 init-declarator-list , init-declarator</pre>
19624 <pre>
19625 declarator
19626 declarator = initializer</pre>
19628 <!--page 424 -->
19629 <pre>
19630 typedef
19631 extern
19632 static
19633 auto
19634 register</pre>
19636 <pre>
19637 void
19638 char
19639 short
19640 int
19641 long
19642 float
19643 double
19644 signed
19645 unsigned
19646 _Bool
19647 _Complex
19648 struct-or-union-specifier *
19649 enum-specifier
19650 typedef-name</pre>
19652 <pre>
19653 struct-or-union identifieropt { struct-declaration-list }
19654 struct-or-union identifier</pre>
19656 <pre>
19657 struct
19658 union</pre>
19660 <pre>
19661 struct-declaration
19662 struct-declaration-list struct-declaration</pre>
19664 <pre>
19665 specifier-qualifier-list struct-declarator-list ;</pre>
19667 <pre>
19668 type-specifier specifier-qualifier-listopt
19669 type-qualifier specifier-qualifier-listopt</pre>
19671 <pre>
19672 struct-declarator
19673 struct-declarator-list , struct-declarator</pre>
19675 <!--page 425 -->
19676 <pre>
19677 declarator
19678 declaratoropt : constant-expression</pre>
19680 <pre>
19681 enum identifieropt { enumerator-list }
19682 enum identifieropt { enumerator-list , }
19683 enum identifier</pre>
19685 <pre>
19686 enumerator
19687 enumerator-list , enumerator</pre>
19689 <pre>
19690 enumeration-constant
19691 enumeration-constant = constant-expression</pre>
19693 <pre>
19694 const
19695 restrict
19696 volatile</pre>
19698 <pre>
19699 inline</pre>
19701 <pre>
19702 pointeropt direct-declarator</pre>
19704 <pre>
19705 identifier
19706 ( declarator )
19707 direct-declarator [ type-qualifier-listopt assignment-expressionopt ]
19708 direct-declarator [ static type-qualifier-listopt assignment-expression ]
19709 direct-declarator [ type-qualifier-list static assignment-expression ]
19710 direct-declarator [ type-qualifier-listopt * ]
19711 direct-declarator ( parameter-type-list )
19712 direct-declarator ( identifier-listopt )</pre>
19714 <pre>
19715 * type-qualifier-listopt
19716 * type-qualifier-listopt pointer</pre>
19718 <pre>
19719 type-qualifier
19720 type-qualifier-list type-qualifier</pre>
19722 <!--page 426 -->
19723 <pre>
19724 parameter-list
19725 parameter-list , ...</pre>
19727 <pre>
19728 parameter-declaration
19729 parameter-list , parameter-declaration</pre>
19731 <pre>
19732 declaration-specifiers declarator
19733 declaration-specifiers abstract-declaratoropt</pre>
19735 <pre>
19736 identifier
19737 identifier-list , identifier</pre>
19739 <pre>
19740 specifier-qualifier-list abstract-declaratoropt</pre>
19742 <pre>
19743 pointer
19744 pointeropt direct-abstract-declarator</pre>
19746 <pre>
19747 ( abstract-declarator )
19748 direct-abstract-declaratoropt [ type-qualifier-listopt
19749 assignment-expressionopt ]
19750 direct-abstract-declaratoropt [ static type-qualifier-listopt
19751 assignment-expression ]
19752 direct-abstract-declaratoropt [ type-qualifier-list static
19753 assignment-expression ]
19754 direct-abstract-declaratoropt [ * ]
19755 direct-abstract-declaratoropt ( parameter-type-listopt )</pre>
19757 <pre>
19758 identifier</pre>
19760 <pre>
19761 assignment-expression
19762 { initializer-list }
19763 { initializer-list , }</pre>
19765 <pre>
19766 designationopt initializer
19767 initializer-list , designationopt initializer</pre>
19769 <!--page 427 -->
19770 <pre>
19771 designator-list =</pre>
19773 <pre>
19774 designator
19775 designator-list designator</pre>
19777 <pre>
19778 [ constant-expression ]
19779 . identifier</pre>
19783 <pre>
19784 labeled-statement
19785 compound-statement
19786 expression-statement
19787 selection-statement
19788 iteration-statement
19789 jump-statement</pre>
19791 <pre>
19792 identifier : statement
19793 case constant-expression : statement
19794 default : statement</pre>
19796 <pre>
19797 { block-item-listopt }</pre>
19799 <pre>
19800 block-item
19801 block-item-list block-item</pre>
19803 <pre>
19804 declaration
19805 statement</pre>
19807 <pre>
19808 expressionopt ;</pre>
19810 <!--page 428 -->
19811 <pre>
19812 if ( expression ) statement
19813 if ( expression ) statement else statement
19814 switch ( expression ) statement</pre>
19816 <pre>
19817 while ( expression ) statement
19818 do statement while ( expression ) ;
19819 for ( expressionopt ; expressionopt ; expressionopt ) statement
19820 for ( declaration expressionopt ; expressionopt ) statement</pre>
19822 <pre>
19823 goto identifier ;
19824 continue ;
19825 break ;
19826 return expressionopt ;</pre>
19830 <pre>
19831 external-declaration
19832 translation-unit external-declaration</pre>
19834 <pre>
19835 function-definition
19836 declaration</pre>
19838 <pre>
19839 declaration-specifiers declarator declaration-listopt compound-statement</pre>
19841 <pre>
19842 declaration
19843 declaration-list declaration</pre>
19847 <pre>
19848 groupopt</pre>
19850 <pre>
19851 group-part
19852 group group-part</pre>
19854 <pre>
19855 if-section
19856 control-line
19857 text-line
19858 # non-directive</pre>
19860 <!--page 429 -->
19861 <pre>
19862 if-group elif-groupsopt else-groupopt endif-line</pre>
19864 <pre>
19865 # if constant-expression new-line groupopt
19866 # ifdef identifier new-line groupopt
19867 # ifndef identifier new-line groupopt</pre>
19869 <pre>
19870 elif-group
19871 elif-groups elif-group</pre>
19873 <pre>
19874 # elif constant-expression new-line groupopt</pre>
19876 <pre>
19877 # else new-line groupopt</pre>
19879 <pre>
19880 # endif new-line</pre>
19882 <pre>
19883 # include pp-tokens new-line
19884 # define identifier replacement-list new-line
19885 # define identifier lparen identifier-listopt )
19886 replacement-list new-line
19887 # define identifier lparen ... ) replacement-list new-line
19888 # define identifier lparen identifier-list , ... )
19889 replacement-list new-line
19890 # undef identifier new-line
19891 # line pp-tokens new-line
19892 # error pp-tokensopt new-line
19893 # pragma pp-tokensopt new-line
19894 # new-line</pre>
19896 <pre>
19897 pp-tokensopt new-line</pre>
19899 <pre>
19900 pp-tokens new-line</pre>
19902 <pre>
19903 a ( character not immediately preceded by white-space</pre>
19905 <!--page 430 -->
19906 <pre>
19907 pp-tokensopt</pre>
19909 <pre>
19910 preprocessing-token
19911 pp-tokens preprocessing-token</pre>
19913 <!--page 431 -->
19914 <pre>
19915 the new-line character</pre>
19918 <pre>
19919 (informative)
19920 Library summary</pre>
19923 <pre>
19924 NDEBUG
19925 void assert(scalar expression);</pre>
19928 <!--page 432 -->
19929 <!--page 433 -->
19930 <pre>
19931 complex imaginary I
19932 _Complex_I _Imaginary_I
19933 #pragma STDC CX_LIMITED_RANGE on-off-switch
19934 double complex cacos(double complex z);
19935 float complex cacosf(float complex z);
19936 long double complex cacosl(long double complex z);
19937 double complex casin(double complex z);
19938 float complex casinf(float complex z);
19939 long double complex casinl(long double complex z);
19940 double complex catan(double complex z);
19941 float complex catanf(float complex z);
19942 long double complex catanl(long double complex z);
19943 double complex ccos(double complex z);
19944 float complex ccosf(float complex z);
19945 long double complex ccosl(long double complex z);
19946 double complex csin(double complex z);
19947 float complex csinf(float complex z);
19948 long double complex csinl(long double complex z);
19949 double complex ctan(double complex z);
19950 float complex ctanf(float complex z);
19951 long double complex ctanl(long double complex z);
19952 double complex cacosh(double complex z);
19953 float complex cacoshf(float complex z);
19954 long double complex cacoshl(long double complex z);
19955 double complex casinh(double complex z);
19956 float complex casinhf(float complex z);
19957 long double complex casinhl(long double complex z);
19958 double complex catanh(double complex z);
19959 float complex catanhf(float complex z);
19960 long double complex catanhl(long double complex z);
19961 double complex ccosh(double complex z);
19962 float complex ccoshf(float complex z);
19963 long double complex ccoshl(long double complex z);
19964 double complex csinh(double complex z);
19965 float complex csinhf(float complex z);
19966 long double complex csinhl(long double complex z);
19967 double complex ctanh(double complex z);
19968 float complex ctanhf(float complex z);
19969 long double complex ctanhl(long double complex z);
19970 double complex cexp(double complex z);
19971 float complex cexpf(float complex z);
19972 long double complex cexpl(long double complex z);
19973 double complex clog(double complex z);
19974 float complex clogf(float complex z);
19975 long double complex clogl(long double complex z);
19976 double cabs(double complex z);
19977 float cabsf(float complex z);
19978 long double cabsl(long double complex z);
19979 double complex cpow(double complex x, double complex y);
19980 float complex cpowf(float complex x, float complex y);
19981 long double complex cpowl(long double complex x,
19982 long double complex y);
19983 double complex csqrt(double complex z);
19984 float complex csqrtf(float complex z);
19985 long double complex csqrtl(long double complex z);
19986 double carg(double complex z);
19987 float cargf(float complex z);
19988 long double cargl(long double complex z);
19989 double cimag(double complex z);
19990 float cimagf(float complex z);
19991 long double cimagl(long double complex z);
19992 double complex conj(double complex z);
19993 float complex conjf(float complex z);
19994 long double complex conjl(long double complex z);
19995 double complex cproj(double complex z);
19996 float complex cprojf(float complex z);
19997 long double complex cprojl(long double complex z);
19998 double creal(double complex z);
19999 float crealf(float complex z);
20000 long double creall(long double complex z);</pre>
20003 <pre>
20004 int isalnum(int c);
20005 int isalpha(int c);
20006 int isblank(int c);
20007 int iscntrl(int c);
20008 int isdigit(int c);
20009 int isgraph(int c);
20010 int islower(int c);
20011 int isprint(int c);
20012 int ispunct(int c);
20013 int isspace(int c);
20014 int isupper(int c);
20015 int isxdigit(int c);
20016 int tolower(int c);
20017 int toupper(int c);</pre>
20020 <pre>
20021 EDOM EILSEQ ERANGE errno</pre>
20024 <!--page 434 -->
20025 <pre>
20026 fenv_t FE_OVERFLOW FE_TOWARDZERO
20027 fexcept_t FE_UNDERFLOW FE_UPWARD
20028 FE_DIVBYZERO FE_ALL_EXCEPT FE_DFL_ENV
20029 FE_INEXACT FE_DOWNWARD
20030 FE_INVALID FE_TONEAREST
20031 #pragma STDC FENV_ACCESS on-off-switch
20032 int feclearexcept(int excepts);
20033 int fegetexceptflag(fexcept_t *flagp, int excepts);
20034 int feraiseexcept(int excepts);
20035 int fesetexceptflag(const fexcept_t *flagp,
20036 int excepts);
20037 int fetestexcept(int excepts);
20038 int fegetround(void);
20039 int fesetround(int round);
20040 int fegetenv(fenv_t *envp);
20041 int feholdexcept(fenv_t *envp);
20042 int fesetenv(const fenv_t *envp);
20043 int feupdateenv(const fenv_t *envp);</pre>
20046 <pre>
20047 FLT_ROUNDS DBL_MIN_EXP FLT_MAX
20048 FLT_EVAL_METHOD LDBL_MIN_EXP DBL_MAX
20049 FLT_RADIX FLT_MIN_10_EXP LDBL_MAX
20050 FLT_MANT_DIG DBL_MIN_10_EXP FLT_EPSILON
20051 DBL_MANT_DIG LDBL_MIN_10_EXP DBL_EPSILON
20052 LDBL_MANT_DIG FLT_MAX_EXP LDBL_EPSILON
20053 DECIMAL_DIG DBL_MAX_EXP FLT_MIN
20054 FLT_DIG LDBL_MAX_EXP DBL_MIN
20055 DBL_DIG FLT_MAX_10_EXP LDBL_MIN
20056 LDBL_DIG DBL_MAX_10_EXP
20057 FLT_MIN_EXP LDBL_MAX_10_EXP</pre>
20060 <!--page 435 -->
20061 <pre>
20062 imaxdiv_t
20063 PRIdN PRIdLEASTN PRIdFASTN PRIdMAX PRIdPTR
20064 PRIiN PRIiLEASTN PRIiFASTN PRIiMAX PRIiPTR
20065 PRIoN PRIoLEASTN PRIoFASTN PRIoMAX PRIoPTR
20066 PRIuN PRIuLEASTN PRIuFASTN PRIuMAX PRIuPTR
20067 PRIxN PRIxLEASTN PRIxFASTN PRIxMAX PRIxPTR
20068 PRIXN PRIXLEASTN PRIXFASTN PRIXMAX PRIXPTR
20069 SCNdN SCNdLEASTN SCNdFASTN SCNdMAX SCNdPTR
20070 SCNiN SCNiLEASTN SCNiFASTN SCNiMAX SCNiPTR
20071 SCNoN SCNoLEASTN SCNoFASTN SCNoMAX SCNoPTR
20072 SCNuN SCNuLEASTN SCNuFASTN SCNuMAX SCNuPTR
20073 SCNxN SCNxLEASTN SCNxFASTN SCNxMAX SCNxPTR
20074 intmax_t imaxabs(intmax_t j);
20075 imaxdiv_t imaxdiv(intmax_t numer, intmax_t denom);
20076 intmax_t strtoimax(const char * restrict nptr,
20077 char ** restrict endptr, int base);
20078 uintmax_t strtoumax(const char * restrict nptr,
20079 char ** restrict endptr, int base);
20080 intmax_t wcstoimax(const wchar_t * restrict nptr,
20081 wchar_t ** restrict endptr, int base);
20082 uintmax_t wcstoumax(const wchar_t * restrict nptr,
20083 wchar_t ** restrict endptr, int base);</pre>
20086 <pre>
20087 and bitor not_eq xor
20088 and_eq compl or xor_eq
20089 bitand not or_eq</pre>
20092 <pre>
20093 CHAR_BIT CHAR_MAX INT_MIN ULONG_MAX
20094 SCHAR_MIN MB_LEN_MAX INT_MAX LLONG_MIN
20095 SCHAR_MAX SHRT_MIN UINT_MAX LLONG_MAX
20096 UCHAR_MAX SHRT_MAX LONG_MIN ULLONG_MAX
20097 CHAR_MIN USHRT_MAX LONG_MAX</pre>
20100 <pre>
20101 struct lconv LC_ALL LC_CTYPE LC_NUMERIC
20102 NULL LC_COLLATE LC_MONETARY LC_TIME
20103 char *setlocale(int category, const char *locale);
20104 struct lconv *localeconv(void);</pre>
20107 <!--page 436 -->
20108 <!--page 437 -->
20109 <!--page 438 -->
20110 <!--page 439 -->
20111 <!--page 440 -->
20112 <pre>
20113 float_t FP_INFINITE FP_FAST_FMAL
20114 double_t FP_NAN FP_ILOGB0
20115 HUGE_VAL FP_NORMAL FP_ILOGBNAN
20116 HUGE_VALF FP_SUBNORMAL MATH_ERRNO
20117 HUGE_VALL FP_ZERO MATH_ERREXCEPT
20118 INFINITY FP_FAST_FMA math_errhandling
20119 NAN FP_FAST_FMAF
20120 #pragma STDC FP_CONTRACT on-off-switch
20121 int fpclassify(real-floating x);
20122 int isfinite(real-floating x);
20123 int isinf(real-floating x);
20124 int isnan(real-floating x);
20125 int isnormal(real-floating x);
20126 int signbit(real-floating x);
20127 double acos(double x);
20128 float acosf(float x);
20129 long double acosl(long double x);
20130 double asin(double x);
20131 float asinf(float x);
20132 long double asinl(long double x);
20133 double atan(double x);
20134 float atanf(float x);
20135 long double atanl(long double x);
20136 double atan2(double y, double x);
20137 float atan2f(float y, float x);
20138 long double atan2l(long double y, long double x);
20139 double cos(double x);
20140 float cosf(float x);
20141 long double cosl(long double x);
20142 double sin(double x);
20143 float sinf(float x);
20144 long double sinl(long double x);
20145 double tan(double x);
20146 float tanf(float x);
20147 long double tanl(long double x);
20148 double acosh(double x);
20149 float acoshf(float x);
20150 long double acoshl(long double x);
20151 double asinh(double x);
20152 float asinhf(float x);
20153 long double asinhl(long double x);
20154 double atanh(double x);
20155 float atanhf(float x);
20156 long double atanhl(long double x);
20157 double cosh(double x);
20158 float coshf(float x);
20159 long double coshl(long double x);
20160 double sinh(double x);
20161 float sinhf(float x);
20162 long double sinhl(long double x);
20163 double tanh(double x);
20164 float tanhf(float x);
20165 long double tanhl(long double x);
20166 double exp(double x);
20167 float expf(float x);
20168 long double expl(long double x);
20169 double exp2(double x);
20170 float exp2f(float x);
20171 long double exp2l(long double x);
20172 double expm1(double x);
20173 float expm1f(float x);
20174 long double expm1l(long double x);
20175 double frexp(double value, int *exp);
20176 float frexpf(float value, int *exp);
20177 long double frexpl(long double value, int *exp);
20178 int ilogb(double x);
20179 int ilogbf(float x);
20180 int ilogbl(long double x);
20181 double ldexp(double x, int exp);
20182 float ldexpf(float x, int exp);
20183 long double ldexpl(long double x, int exp);
20184 double log(double x);
20185 float logf(float x);
20186 long double logl(long double x);
20187 double log10(double x);
20188 float log10f(float x);
20189 long double log10l(long double x);
20190 double log1p(double x);
20191 float log1pf(float x);
20192 long double log1pl(long double x);
20193 double log2(double x);
20194 float log2f(float x);
20195 long double log2l(long double x);
20196 double logb(double x);
20197 float logbf(float x);
20198 long double logbl(long double x);
20199 double modf(double value, double *iptr);
20200 float modff(float value, float *iptr);
20201 long double modfl(long double value, long double *iptr);
20202 double scalbn(double x, int n);
20203 float scalbnf(float x, int n);
20204 long double scalbnl(long double x, int n);
20205 double scalbln(double x, long int n);
20206 float scalblnf(float x, long int n);
20207 long double scalblnl(long double x, long int n);
20208 double cbrt(double x);
20209 float cbrtf(float x);
20210 long double cbrtl(long double x);
20211 double fabs(double x);
20212 float fabsf(float x);
20213 long double fabsl(long double x);
20214 double hypot(double x, double y);
20215 float hypotf(float x, float y);
20216 long double hypotl(long double x, long double y);
20217 double pow(double x, double y);
20218 float powf(float x, float y);
20219 long double powl(long double x, long double y);
20220 double sqrt(double x);
20221 float sqrtf(float x);
20222 long double sqrtl(long double x);
20223 double erf(double x);
20224 float erff(float x);
20225 long double erfl(long double x);
20226 double erfc(double x);
20227 float erfcf(float x);
20228 long double erfcl(long double x);
20229 double lgamma(double x);
20230 float lgammaf(float x);
20231 long double lgammal(long double x);
20232 double tgamma(double x);
20233 float tgammaf(float x);
20234 long double tgammal(long double x);
20235 double ceil(double x);
20236 float ceilf(float x);
20237 long double ceill(long double x);
20238 double floor(double x);
20239 float floorf(float x);
20240 long double floorl(long double x);
20241 double nearbyint(double x);
20242 float nearbyintf(float x);
20243 long double nearbyintl(long double x);
20244 double rint(double x);
20245 float rintf(float x);
20246 long double rintl(long double x);
20247 long int lrint(double x);
20248 long int lrintf(float x);
20249 long int lrintl(long double x);
20250 long long int llrint(double x);
20251 long long int llrintf(float x);
20252 long long int llrintl(long double x);
20253 double round(double x);
20254 float roundf(float x);
20255 long double roundl(long double x);
20256 long int lround(double x);
20257 long int lroundf(float x);
20258 long int lroundl(long double x);
20259 long long int llround(double x);
20260 long long int llroundf(float x);
20261 long long int llroundl(long double x);
20262 double trunc(double x);
20263 float truncf(float x);
20264 long double truncl(long double x);
20265 double fmod(double x, double y);
20266 float fmodf(float x, float y);
20267 long double fmodl(long double x, long double y);
20268 double remainder(double x, double y);
20269 float remainderf(float x, float y);
20270 long double remainderl(long double x, long double y);
20271 double remquo(double x, double y, int *quo);
20272 float remquof(float x, float y, int *quo);
20273 long double remquol(long double x, long double y,
20274 int *quo);
20275 double copysign(double x, double y);
20276 float copysignf(float x, float y);
20277 long double copysignl(long double x, long double y);
20278 double nan(const char *tagp);
20279 float nanf(const char *tagp);
20280 long double nanl(const char *tagp);
20281 double nextafter(double x, double y);
20282 float nextafterf(float x, float y);
20283 long double nextafterl(long double x, long double y);
20284 double nexttoward(double x, long double y);
20285 float nexttowardf(float x, long double y);
20286 long double nexttowardl(long double x, long double y);
20287 double fdim(double x, double y);
20288 float fdimf(float x, float y);
20289 long double fdiml(long double x, long double y);
20290 double fmax(double x, double y);
20291 float fmaxf(float x, float y);
20292 long double fmaxl(long double x, long double y);
20293 double fmin(double x, double y);
20294 float fminf(float x, float y);
20295 long double fminl(long double x, long double y);
20296 double fma(double x, double y, double z);
20297 float fmaf(float x, float y, float z);
20298 long double fmal(long double x, long double y,
20299 long double z);
20300 int isgreater(real-floating x, real-floating y);
20301 int isgreaterequal(real-floating x, real-floating y);
20302 int isless(real-floating x, real-floating y);
20303 int islessequal(real-floating x, real-floating y);
20304 int islessgreater(real-floating x, real-floating y);
20305 int isunordered(real-floating x, real-floating y);</pre>
20308 <pre>
20309 jmp_buf
20310 int setjmp(jmp_buf env);
20311 void longjmp(jmp_buf env, int val);</pre>
20314 <pre>
20315 sig_atomic_t SIG_IGN SIGILL SIGTERM
20316 SIG_DFL SIGABRT SIGINT
20317 SIG_ERR SIGFPE SIGSEGV
20318 void (*signal(int sig, void (*func)(int)))(int);
20319 int raise(int sig);</pre>
20322 <pre>
20323 va_list
20324 type va_arg(va_list ap, type);
20325 void va_copy(va_list dest, va_list src);
20326 void va_end(va_list ap);
20327 void va_start(va_list ap, parmN);</pre>
20330 <!--page 441 -->
20331 <pre>
20332 bool
20333 true
20334 false
20335 __bool_true_false_are_defined</pre>
20338 <pre>
20339 ptrdiff_t size_t wchar_t NULL
20340 offsetof(type, member-designator)</pre>
20343 <pre>
20344 intN_t INT_LEASTN_MIN PTRDIFF_MAX
20345 uintN_t INT_LEASTN_MAX SIG_ATOMIC_MIN
20346 int_leastN_t UINT_LEASTN_MAX SIG_ATOMIC_MAX
20347 uint_leastN_t INT_FASTN_MIN SIZE_MAX
20348 int_fastN_t INT_FASTN_MAX WCHAR_MIN
20349 uint_fastN_t UINT_FASTN_MAX WCHAR_MAX
20350 intptr_t INTPTR_MIN WINT_MIN
20351 uintptr_t INTPTR_MAX WINT_MAX
20352 intmax_t UINTPTR_MAX INTN_C(value)
20353 uintmax_t INTMAX_MIN UINTN_C(value)
20354 INTN_MIN INTMAX_MAX INTMAX_C(value)
20355 INTN_MAX UINTMAX_MAX UINTMAX_C(value)
20356 UINTN_MAX PTRDIFF_MIN</pre>
20359 <!--page 442 -->
20360 <!--page 443 -->
20361 <pre>
20362 size_t _IOLBF FILENAME_MAX TMP_MAX
20363 FILE _IONBF L_tmpnam stderr
20364 fpos_t BUFSIZ SEEK_CUR stdin
20365 NULL EOF SEEK_END stdout
20366 _IOFBF FOPEN_MAX SEEK_SET
20367 int remove(const char *filename);
20368 int rename(const char *old, const char *new);
20369 FILE *tmpfile(void);
20370 char *tmpnam(char *s);
20371 int fclose(FILE *stream);
20372 int fflush(FILE *stream);
20373 FILE *fopen(const char * restrict filename,
20374 const char * restrict mode);
20375 FILE *freopen(const char * restrict filename,
20376 const char * restrict mode,
20377 FILE * restrict stream);
20378 void setbuf(FILE * restrict stream,
20379 char * restrict buf);
20380 int setvbuf(FILE * restrict stream,
20381 char * restrict buf,
20382 int mode, size_t size);
20383 int fprintf(FILE * restrict stream,
20384 const char * restrict format, ...);
20385 int fscanf(FILE * restrict stream,
20386 const char * restrict format, ...);
20387 int printf(const char * restrict format, ...);
20388 int scanf(const char * restrict format, ...);
20389 int snprintf(char * restrict s, size_t n,
20390 const char * restrict format, ...);
20391 int sprintf(char * restrict s,
20392 const char * restrict format, ...);
20393 int sscanf(const char * restrict s,
20394 const char * restrict format, ...);
20395 int vfprintf(FILE * restrict stream,
20396 const char * restrict format, va_list arg);
20397 int vfscanf(FILE * restrict stream,
20398 const char * restrict format, va_list arg);
20399 int vprintf(const char * restrict format, va_list arg);
20400 int vscanf(const char * restrict format, va_list arg);
20401 int vsnprintf(char * restrict s, size_t n,
20402 const char * restrict format, va_list arg);
20403 int vsprintf(char * restrict s,
20404 const char * restrict format, va_list arg);
20405 int vsscanf(const char * restrict s,
20406 const char * restrict format, va_list arg);
20407 int fgetc(FILE *stream);
20408 char *fgets(char * restrict s, int n,
20409 FILE * restrict stream);
20410 int fputc(int c, FILE *stream);
20411 int fputs(const char * restrict s,
20412 FILE * restrict stream);
20413 int getc(FILE *stream);
20414 int getchar(void);
20415 char *gets(char *s);
20416 int putc(int c, FILE *stream);
20417 int putchar(int c);
20418 int puts(const char *s);
20419 int ungetc(int c, FILE *stream);
20420 size_t fread(void * restrict ptr,
20421 size_t size, size_t nmemb,
20422 FILE * restrict stream);
20423 size_t fwrite(const void * restrict ptr,
20424 size_t size, size_t nmemb,
20425 FILE * restrict stream);
20426 int fgetpos(FILE * restrict stream,
20427 fpos_t * restrict pos);
20428 int fseek(FILE *stream, long int offset, int whence);
20429 int fsetpos(FILE *stream, const fpos_t *pos);
20430 long int ftell(FILE *stream);
20431 void rewind(FILE *stream);
20432 void clearerr(FILE *stream);
20433 int feof(FILE *stream);
20434 int ferror(FILE *stream);
20435 void perror(const char *s);</pre>
20438 <!--page 444 -->
20439 <!--page 445 -->
20440 <pre>
20441 size_t ldiv_t EXIT_FAILURE MB_CUR_MAX
20442 wchar_t lldiv_t EXIT_SUCCESS
20443 div_t NULL RAND_MAX
20444 double atof(const char *nptr);
20445 int atoi(const char *nptr);
20446 long int atol(const char *nptr);
20447 long long int atoll(const char *nptr);
20448 double strtod(const char * restrict nptr,
20449 char ** restrict endptr);
20450 float strtof(const char * restrict nptr,
20451 char ** restrict endptr);
20452 long double strtold(const char * restrict nptr,
20453 char ** restrict endptr);
20454 long int strtol(const char * restrict nptr,
20455 char ** restrict endptr, int base);
20456 long long int strtoll(const char * restrict nptr,
20457 char ** restrict endptr, int base);
20458 unsigned long int strtoul(
20459 const char * restrict nptr,
20460 char ** restrict endptr, int base);
20461 unsigned long long int strtoull(
20462 const char * restrict nptr,
20463 char ** restrict endptr, int base);
20464 int rand(void);
20465 void srand(unsigned int seed);
20466 void *calloc(size_t nmemb, size_t size);
20467 void free(void *ptr);
20468 void *malloc(size_t size);
20469 void *realloc(void *ptr, size_t size);
20470 void abort(void);
20471 int atexit(void (*func)(void));
20472 void exit(int status);
20473 void _Exit(int status);
20474 char *getenv(const char *name);
20475 int system(const char *string);
20476 void *bsearch(const void *key, const void *base,
20477 size_t nmemb, size_t size,
20478 int (*compar)(const void *, const void *));
20479 void qsort(void *base, size_t nmemb, size_t size,
20480 int (*compar)(const void *, const void *));
20481 int abs(int j);
20482 long int labs(long int j);
20483 long long int llabs(long long int j);
20484 div_t div(int numer, int denom);
20485 ldiv_t ldiv(long int numer, long int denom);
20486 lldiv_t lldiv(long long int numer,
20487 long long int denom);
20488 int mblen(const char *s, size_t n);
20489 int mbtowc(wchar_t * restrict pwc,
20490 const char * restrict s, size_t n);
20491 int wctomb(char *s, wchar_t wchar);
20492 size_t mbstowcs(wchar_t * restrict pwcs,
20493 const char * restrict s, size_t n);
20494 size_t wcstombs(char * restrict s,
20495 const wchar_t * restrict pwcs, size_t n);</pre>
20498 <!--page 446 -->
20499 <pre>
20500 size_t
20501 NULL
20502 void *memcpy(void * restrict s1,
20503 const void * restrict s2, size_t n);
20504 void *memmove(void *s1, const void *s2, size_t n);
20505 char *strcpy(char * restrict s1,
20506 const char * restrict s2);
20507 char *strncpy(char * restrict s1,
20508 const char * restrict s2, size_t n);
20509 char *strcat(char * restrict s1,
20510 const char * restrict s2);
20511 char *strncat(char * restrict s1,
20512 const char * restrict s2, size_t n);
20513 int memcmp(const void *s1, const void *s2, size_t n);
20514 int strcmp(const char *s1, const char *s2);
20515 int strcoll(const char *s1, const char *s2);
20516 int strncmp(const char *s1, const char *s2, size_t n);
20517 size_t strxfrm(char * restrict s1,
20518 const char * restrict s2, size_t n);
20519 void *memchr(const void *s, int c, size_t n);
20520 char *strchr(const char *s, int c);
20521 size_t strcspn(const char *s1, const char *s2);
20522 char *strpbrk(const char *s1, const char *s2);
20523 char *strrchr(const char *s, int c);
20524 size_t strspn(const char *s1, const char *s2);
20525 char *strstr(const char *s1, const char *s2);
20526 char *strtok(char * restrict s1,
20527 const char * restrict s2);
20528 void *memset(void *s, int c, size_t n);
20529 char *strerror(int errnum);
20530 size_t strlen(const char *s);</pre>
20533 <pre>
20534 acos sqrt fmod nextafter
20535 asin fabs frexp nexttoward
20536 atan atan2 hypot remainder
20537 acosh cbrt ilogb remquo
20538 asinh ceil ldexp rint
20539 atanh copysign lgamma round
20540 cos erf llrint scalbn
20541 sin erfc llround scalbln
20542 tan exp2 log10 tgamma
20543 cosh expm1 log1p trunc
20544 sinh fdim log2 carg
20545 tanh floor logb cimag
20546 exp fma lrint conj
20547 log fmax lround cproj
20548 pow fmin nearbyint creal</pre>
20551 <!--page 447 -->
20552 <pre>
20553 NULL size_t time_t
20554 CLOCKS_PER_SEC clock_t struct tm
20555 clock_t clock(void);
20556 double difftime(time_t time1, time_t time0);
20557 time_t mktime(struct tm *timeptr);
20558 time_t time(time_t *timer);
20559 char *asctime(const struct tm *timeptr);
20560 char *ctime(const time_t *timer);
20561 struct tm *gmtime(const time_t *timer);
20562 struct tm *localtime(const time_t *timer);
20563 size_t strftime(char * restrict s,
20564 size_t maxsize,
20565 const char * restrict format,
20566 const struct tm * restrict timeptr);</pre>
20568 <h3><a name="B.23" href="#B.23">B.23 Extended multibyte/wide character utilities <wchar.h></a></h3>
20569 <!--page 448 -->
20570 <!--page 449 -->
20571 <pre>
20572 wchar_t wint_t WCHAR_MAX
20573 size_t struct tm WCHAR_MIN
20574 mbstate_t NULL WEOF
20575 int fwprintf(FILE * restrict stream,
20576 const wchar_t * restrict format, ...);
20577 int fwscanf(FILE * restrict stream,
20578 const wchar_t * restrict format, ...);
20579 int swprintf(wchar_t * restrict s, size_t n,
20580 const wchar_t * restrict format, ...);
20581 int swscanf(const wchar_t * restrict s,
20582 const wchar_t * restrict format, ...);
20583 int vfwprintf(FILE * restrict stream,
20584 const wchar_t * restrict format, va_list arg);
20585 int vfwscanf(FILE * restrict stream,
20586 const wchar_t * restrict format, va_list arg);
20587 int vswprintf(wchar_t * restrict s, size_t n,
20588 const wchar_t * restrict format, va_list arg);
20589 int vswscanf(const wchar_t * restrict s,
20590 const wchar_t * restrict format, va_list arg);
20591 int vwprintf(const wchar_t * restrict format,
20592 va_list arg);
20593 int vwscanf(const wchar_t * restrict format,
20594 va_list arg);
20595 int wprintf(const wchar_t * restrict format, ...);
20596 int wscanf(const wchar_t * restrict format, ...);
20597 wint_t fgetwc(FILE *stream);
20598 wchar_t *fgetws(wchar_t * restrict s, int n,
20599 FILE * restrict stream);
20600 wint_t fputwc(wchar_t c, FILE *stream);
20601 int fputws(const wchar_t * restrict s,
20602 FILE * restrict stream);
20603 int fwide(FILE *stream, int mode);
20604 wint_t getwc(FILE *stream);
20605 wint_t getwchar(void);
20606 wint_t putwc(wchar_t c, FILE *stream);
20607 wint_t putwchar(wchar_t c);
20608 wint_t ungetwc(wint_t c, FILE *stream);
20609 double wcstod(const wchar_t * restrict nptr,
20610 wchar_t ** restrict endptr);
20611 float wcstof(const wchar_t * restrict nptr,
20612 wchar_t ** restrict endptr);
20613 long double wcstold(const wchar_t * restrict nptr,
20614 wchar_t ** restrict endptr);
20615 long int wcstol(const wchar_t * restrict nptr,
20616 wchar_t ** restrict endptr, int base);
20617 long long int wcstoll(const wchar_t * restrict nptr,
20618 wchar_t ** restrict endptr, int base);
20619 unsigned long int wcstoul(const wchar_t * restrict nptr,
20620 wchar_t ** restrict endptr, int base);
20621 unsigned long long int wcstoull(
20622 const wchar_t * restrict nptr,
20623 wchar_t ** restrict endptr, int base);
20624 wchar_t *wcscpy(wchar_t * restrict s1,
20625 const wchar_t * restrict s2);
20626 wchar_t *wcsncpy(wchar_t * restrict s1,
20627 const wchar_t * restrict s2, size_t n);
20628 wchar_t *wmemcpy(wchar_t * restrict s1,
20629 const wchar_t * restrict s2, size_t n);
20630 wchar_t *wmemmove(wchar_t *s1, const wchar_t *s2,
20631 size_t n);
20632 wchar_t *wcscat(wchar_t * restrict s1,
20633 const wchar_t * restrict s2);
20634 wchar_t *wcsncat(wchar_t * restrict s1,
20635 const wchar_t * restrict s2, size_t n);
20636 int wcscmp(const wchar_t *s1, const wchar_t *s2);
20637 int wcscoll(const wchar_t *s1, const wchar_t *s2);
20638 int wcsncmp(const wchar_t *s1, const wchar_t *s2,
20639 size_t n);
20640 size_t wcsxfrm(wchar_t * restrict s1,
20641 const wchar_t * restrict s2, size_t n);
20642 int wmemcmp(const wchar_t *s1, const wchar_t *s2,
20643 size_t n);
20644 wchar_t *wcschr(const wchar_t *s, wchar_t c);
20645 size_t wcscspn(const wchar_t *s1, const wchar_t *s2);
20646 wchar_t *wcspbrk(const wchar_t *s1, const wchar_t *s2); *
20647 wchar_t *wcsrchr(const wchar_t *s, wchar_t c);
20648 size_t wcsspn(const wchar_t *s1, const wchar_t *s2);
20649 wchar_t *wcsstr(const wchar_t *s1, const wchar_t *s2);
20650 wchar_t *wcstok(wchar_t * restrict s1,
20651 const wchar_t * restrict s2,
20652 wchar_t ** restrict ptr);
20653 wchar_t *wmemchr(const wchar_t *s, wchar_t c, size_t n);
20654 size_t wcslen(const wchar_t *s);
20655 wchar_t *wmemset(wchar_t *s, wchar_t c, size_t n);
20656 size_t wcsftime(wchar_t * restrict s, size_t maxsize,
20657 const wchar_t * restrict format,
20658 const struct tm * restrict timeptr);
20659 wint_t btowc(int c);
20660 int wctob(wint_t c);
20661 int mbsinit(const mbstate_t *ps);
20662 size_t mbrlen(const char * restrict s, size_t n,
20663 mbstate_t * restrict ps);
20664 size_t mbrtowc(wchar_t * restrict pwc,
20665 const char * restrict s, size_t n,
20666 mbstate_t * restrict ps);
20667 size_t wcrtomb(char * restrict s, wchar_t wc,
20668 mbstate_t * restrict ps);
20669 size_t mbsrtowcs(wchar_t * restrict dst,
20670 const char ** restrict src, size_t len,
20671 mbstate_t * restrict ps);
20672 size_t wcsrtombs(char * restrict dst,
20673 const wchar_t ** restrict src, size_t len,
20674 mbstate_t * restrict ps);</pre>
20676 <h3><a name="B.24" href="#B.24">B.24 Wide character classification and mapping utilities <wctype.h></a></h3>
20677 <!--page 450 -->
20678 <!--page 451 -->
20679 <pre>
20680 wint_t wctrans_t wctype_t WEOF
20681 int iswalnum(wint_t wc);
20682 int iswalpha(wint_t wc);
20683 int iswblank(wint_t wc);
20684 int iswcntrl(wint_t wc);
20685 int iswdigit(wint_t wc);
20686 int iswgraph(wint_t wc);
20687 int iswlower(wint_t wc);
20688 int iswprint(wint_t wc);
20689 int iswpunct(wint_t wc);
20690 int iswspace(wint_t wc);
20691 int iswupper(wint_t wc);
20692 int iswxdigit(wint_t wc);
20693 int iswctype(wint_t wc, wctype_t desc);
20694 wctype_t wctype(const char *property);
20695 wint_t towlower(wint_t wc);
20696 wint_t towupper(wint_t wc);
20697 wint_t towctrans(wint_t wc, wctrans_t desc);
20698 wctrans_t wctrans(const char *property);</pre>
20701 <p><!--para 1 -->
20702 <pre>
20703 (informative)
20704 Sequence points</pre>
20706 <ul>
20707 <li> The call to a function, after the arguments have been evaluated (<a href="#6.5.2.2">6.5.2.2</a>).
20708 <li> The end of the first operand of the following operators: logical AND && (<a href="#6.5.13">6.5.13</a>);
20709 logical OR || (<a href="#6.5.14">6.5.14</a>); conditional ? (<a href="#6.5.15">6.5.15</a>); comma , (<a href="#6.5.17">6.5.17</a>).
20711 <li> The end of a full expression: an initializer (<a href="#6.7.8">6.7.8</a>); the expression in an expression
20712 statement (<a href="#6.8.3">6.8.3</a>); the controlling expression of a selection statement (if or switch)
20713 (<a href="#6.8.4">6.8.4</a>); the controlling expression of a while or do statement (<a href="#6.8.5">6.8.5</a>); each of the
20714 expressions of a for statement (<a href="#6.8.5.3">6.8.5.3</a>); the expression in a return statement
20717 <li> After the actions associated with each formatted input/output function conversion
20719 <li> Immediately before and immediately after each call to a comparison function, and
20720 also between any call to a comparison function and any movement of the objects
20722 <!--page 452 -->
20723 </ul>
20726 <p><!--para 1 -->
20727 <pre>
20728 (normative)
20729 Universal character names for identifiers</pre>
20730 This clause lists the hexadecimal code values that are valid in universal character names
20731 in identifiers.
20732 <p><!--para 2 -->
20733 This table is reproduced unchanged from ISO/IEC TR 10176:1998, produced by ISO/IEC
20734 JTC 1/SC 22/WG 20, except for the omission of ranges that are part of the basic character
20735 sets.
20736 Latin: 00AA, 00BA, 00C0-00D6, 00D8-00F6, 00F8-01F5, 01FA-0217,
20737 <pre>
20738 0250-02A8, 1E00-1E9B, 1EA0-1EF9, 207F</pre>
20739 Greek: 0386, 0388-038A, 038C, 038E-03A1, 03A3-03CE, 03D0-03D6,
20740 <pre>
20741 03DA, 03DC, 03DE, 03E0, 03E2-03F3, 1F00-1F15, 1F18-1F1D,
20742 1F20-1F45, 1F48-1F4D, 1F50-1F57, 1F59, 1F5B, 1F5D,
20743 1F5F-1F7D, 1F80-1FB4, 1FB6-1FBC, 1FC2-1FC4, 1FC6-1FCC,
20744 1FD0-1FD3, 1FD6-1FDB, 1FE0-1FEC, 1FF2-1FF4, 1FF6-1FFC</pre>
20745 Cyrillic: 0401-040C, 040E-044F, 0451-045C, 045E-0481, 0490-04C4,
20746 <pre>
20747 04C7-04C8, 04CB-04CC, 04D0-04EB, 04EE-04F5, 04F8-04F9</pre>
20748 Armenian: 0531-0556, 0561-0587
20749 Hebrew: 05B0-05B9, 05BB-05BD, 05BF, 05C1-05C2, 05D0-05EA,
20750 <pre>
20751 05F0-05F2</pre>
20752 Arabic: 0621-063A, 0640-0652, 0670-06B7, 06BA-06BE, 06C0-06CE,
20753 <pre>
20754 06D0-06DC, 06E5-06E8, 06EA-06ED</pre>
20755 Devanagari: 0901-0903, 0905-0939, 093E-094D, 0950-0952, 0958-0963
20756 Bengali: 0981-0983, 0985-098C, 098F-0990, 0993-09A8, 09AA-09B0,
20757 <pre>
20758 09B2, 09B6-09B9, 09BE-09C4, 09C7-09C8, 09CB-09CD,
20759 09DC-09DD, 09DF-09E3, 09F0-09F1</pre>
20760 Gurmukhi: 0A02, 0A05-0A0A, 0A0F-0A10, 0A13-0A28, 0A2A-0A30,
20761 <pre>
20762 0A32-0A33, 0A35-0A36, 0A38-0A39, 0A3E-0A42, 0A47-0A48,
20763 0A4B-0A4D, 0A59-0A5C, 0A5E, 0A74</pre>
20764 Gujarati: 0A81-0A83, 0A85-0A8B, 0A8D, 0A8F-0A91, 0A93-0AA8,
20765 <pre>
20766 0AAA-0AB0, 0AB2-0AB3, 0AB5-0AB9, 0ABD-0AC5,
20767 0AC7-0AC9, 0ACB-0ACD, 0AD0, 0AE0</pre>
20768 Oriya: 0B01-0B03, 0B05-0B0C, 0B0F-0B10, 0B13-0B28, 0B2A-0B30,
20769 <!--page 453 -->
20770 <pre>
20771 0B32-0B33, 0B36-0B39, 0B3E-0B43, 0B47-0B48, 0B4B-0B4D,
20772 0B5C-0B5D, 0B5F-0B61</pre>
20773 Tamil: 0B82-0B83, 0B85-0B8A, 0B8E-0B90, 0B92-0B95, 0B99-0B9A,
20774 <pre>
20775 0B9C, 0B9E-0B9F, 0BA3-0BA4, 0BA8-0BAA, 0BAE-0BB5,
20776 0BB7-0BB9, 0BBE-0BC2, 0BC6-0BC8, 0BCA-0BCD</pre>
20777 Telugu: 0C01-0C03, 0C05-0C0C, 0C0E-0C10, 0C12-0C28, 0C2A-0C33,
20778 <pre>
20779 0C35-0C39, 0C3E-0C44, 0C46-0C48, 0C4A-0C4D, 0C60-0C61</pre>
20780 Kannada: 0C82-0C83, 0C85-0C8C, 0C8E-0C90, 0C92-0CA8, 0CAA-0CB3,
20781 <pre>
20782 0CB5-0CB9, 0CBE-0CC4, 0CC6-0CC8, 0CCA-0CCD, 0CDE,
20783 0CE0-0CE1</pre>
20784 Malayalam: 0D02-0D03, 0D05-0D0C, 0D0E-0D10, 0D12-0D28, 0D2A-0D39,
20785 <pre>
20786 0D3E-0D43, 0D46-0D48, 0D4A-0D4D, 0D60-0D61</pre>
20787 Thai: 0E01-0E3A, 0E40-0E5B
20788 Lao: 0E81-0E82, 0E84, 0E87-0E88, 0E8A, 0E8D, 0E94-0E97,
20789 <pre>
20790 0E99-0E9F, 0EA1-0EA3, 0EA5, 0EA7, 0EAA-0EAB,
20791 0EAD-0EAE, 0EB0-0EB9, 0EBB-0EBD, 0EC0-0EC4, 0EC6,
20792 0EC8-0ECD, 0EDC-0EDD</pre>
20793 Tibetan: 0F00, 0F18-0F19, 0F35, 0F37, 0F39, 0F3E-0F47, 0F49-0F69,
20794 <pre>
20795 0F71-0F84, 0F86-0F8B, 0F90-0F95, 0F97, 0F99-0FAD,
20796 0FB1-0FB7, 0FB9</pre>
20797 Georgian: 10A0-10C5, 10D0-10F6
20798 Hiragana: 3041-3093, 309B-309C
20799 Katakana: 30A1-30F6, 30FB-30FC
20800 Bopomofo: 3105-312C
20801 CJK Unified Ideographs: 4E00-9FA5
20802 Hangul: AC00-D7A3
20803 Digits: 0660-0669, 06F0-06F9, 0966-096F, 09E6-09EF, 0A66-0A6F,
20804 <pre>
20805 0AE6-0AEF, 0B66-0B6F, 0BE7-0BEF, 0C66-0C6F, 0CE6-0CEF,
20806 0D66-0D6F, 0E50-0E59, 0ED0-0ED9, 0F20-0F33</pre>
20807 Special characters: 00B5, 00B7, 02B0-02B8, 02BB, 02BD-02C1, 02D0-02D1,
20808 <!--page 454 -->
20809 <pre>
20810 02E0-02E4, 037A, 0559, 093D, 0B3D, 1FBE, 203F-2040, 2102,
20811 2107, 210A-2113, 2115, 2118-211D, 2124, 2126, 2128, 212A-2131,
20812 2133-2138, 2160-2182, 3005-3007, 3021-3029</pre>
20815 <p><!--para 1 -->
20816 <pre>
20817 (informative)
20818 Implementation limits</pre>
20819 The contents of the header <a href="#7.10"><limits.h></a> are given below, in alphabetical order. The
20820 minimum magnitudes shown shall be replaced by implementation-defined magnitudes
20821 with the same sign. The values shall all be constant expressions suitable for use in #if
20822 preprocessing directives. The components are described further in <a href="#5.2.4.2.1">5.2.4.2.1</a>.
20823 <p><!--para 2 -->
20824 <pre>
20825 #define CHAR_BIT 8
20826 #define CHAR_MAX UCHAR_MAX or SCHAR_MAX
20827 #define CHAR_MIN 0 or SCHAR_MIN
20828 #define INT_MAX +32767
20829 #define INT_MIN -32767
20830 #define LONG_MAX +2147483647
20831 #define LONG_MIN -2147483647
20832 #define LLONG_MAX +9223372036854775807
20833 #define LLONG_MIN -9223372036854775807
20834 #define MB_LEN_MAX 1
20835 #define SCHAR_MAX +127
20836 #define SCHAR_MIN -127
20837 #define SHRT_MAX +32767
20838 #define SHRT_MIN -32767
20839 #define UCHAR_MAX 255
20840 #define USHRT_MAX 65535
20841 #define UINT_MAX 65535
20842 #define ULONG_MAX 4294967295
20843 #define ULLONG_MAX 18446744073709551615</pre>
20844 The contents of the header <a href="#7.7"><float.h></a> are given below. All integer values, except
20845 FLT_ROUNDS, shall be constant expressions suitable for use in #if preprocessing
20846 directives; all floating values shall be constant expressions. The components are
20848 <p><!--para 3 -->
20849 The values given in the following list shall be replaced by implementation-defined
20850 expressions:
20851 <p><!--para 4 -->
20852 <pre>
20853 #define FLT_EVAL_METHOD
20854 #define FLT_ROUNDS</pre>
20855 The values given in the following list shall be replaced by implementation-defined
20856 constant expressions that are greater or equal in magnitude (absolute value) to those
20857 shown, with the same sign:
20858 <!--page 455 -->
20859 <p><!--para 5 -->
20860 <pre>
20861 #define DBL_DIG 10
20862 #define DBL_MANT_DIG
20863 #define DBL_MAX_10_EXP +37
20864 #define DBL_MAX_EXP
20865 #define DBL_MIN_10_EXP -37
20866 #define DBL_MIN_EXP
20867 #define DECIMAL_DIG 10
20868 #define FLT_DIG 6
20869 #define FLT_MANT_DIG
20870 #define FLT_MAX_10_EXP +37
20871 #define FLT_MAX_EXP
20872 #define FLT_MIN_10_EXP -37
20873 #define FLT_MIN_EXP
20874 #define FLT_RADIX 2
20875 #define LDBL_DIG 10
20876 #define LDBL_MANT_DIG
20877 #define LDBL_MAX_10_EXP +37
20878 #define LDBL_MAX_EXP
20879 #define LDBL_MIN_10_EXP -37
20880 #define LDBL_MIN_EXP</pre>
20881 The values given in the following list shall be replaced by implementation-defined
20882 constant expressions with values that are greater than or equal to those shown:
20883 <p><!--para 6 -->
20884 <pre>
20885 #define DBL_MAX 1E+37
20886 #define FLT_MAX 1E+37
20887 #define LDBL_MAX 1E+37</pre>
20888 The values given in the following list shall be replaced by implementation-defined
20889 constant expressions with (positive) values that are less than or equal to those shown:
20890 <!--page 456 -->
20891 <pre>
20892 #define DBL_EPSILON 1E-9
20893 #define DBL_MIN 1E-37
20894 #define FLT_EPSILON 1E-5
20895 #define FLT_MIN 1E-37
20896 #define LDBL_EPSILON 1E-9
20897 #define LDBL_MIN 1E-37</pre>
20900 <pre>
20901 (normative)
20902 IEC 60559 floating-point arithmetic</pre>
20905 <p><!--para 1 -->
20906 This annex specifies C language support for the IEC 60559 floating-point standard. The
20907 IEC 60559 floating-point standard is specifically Binary floating-point arithmetic for
20908 microprocessor systems, second edition (IEC 60559:1989), previously designated
20909 IEC 559:1989 and as IEEE Standard for Binary Floating-Point Arithmetic
20910 (ANSI/IEEE 754-1985). IEEE Standard for Radix-Independent Floating-Point
20911 Arithmetic (ANSI/IEEE 854-1987) generalizes the binary standard to remove
20912 dependencies on radix and word length. IEC 60559 generally refers to the floating-point
20913 standard, as in IEC 60559 operation, IEC 60559 format, etc. An implementation that
20914 defines __STDC_IEC_559__ shall conform to the specifications in this annex. Where
20915 a binding between the C language and IEC 60559 is indicated, the IEC 60559-specified
20916 behavior is adopted by reference, unless stated otherwise.
20919 <p><!--para 1 -->
20920 The C floating types match the IEC 60559 formats as follows:
20921 <ul>
20922 <li> The float type matches the IEC 60559 single format.
20923 <li> The double type matches the IEC 60559 double format.
20924 <li> The long double type matches an IEC 60559 extended format,<sup><a href="#note307"><b>307)</b></a></sup> else a
20925 non-IEC 60559 extended format, else the IEC 60559 double format.
20926 </ul>
20927 Any non-IEC 60559 extended format used for the long double type shall have more
20928 precision than IEC 60559 double and at least the range of IEC 60559 double.<sup><a href="#note308"><b>308)</b></a></sup>
20929 Recommended practice
20930 <p><!--para 2 -->
20931 The long double type should match an IEC 60559 extended format.
20936 <!--page 457 -->
20938 <h6>footnotes</h6>
20939 <p><small><a name="note307" href="#note307">307)</a> ''Extended'' is IEC 60559's double-extended data format. Extended refers to both the common 80-bit
20940 and quadruple 128-bit IEC 60559 formats.
20941 </small>
20942 <p><small><a name="note308" href="#note308">308)</a> A non-IEC 60559 long double type is required to provide infinity and NaNs, as its values include
20943 all double values.
20944 </small>
20947 <p><!--para 1 -->
20948 This specification does not define the behavior of signaling NaNs.<sup><a href="#note309"><b>309)</b></a></sup> It generally uses
20949 the term NaN to denote quiet NaNs. The NAN and INFINITY macros and the nan
20950 functions in <a href="#7.12"><math.h></a> provide designations for IEC 60559 NaNs and infinities.
20952 <h6>footnotes</h6>
20953 <p><small><a name="note309" href="#note309">309)</a> Since NaNs created by IEC 60559 operations are always quiet, quiet NaNs (along with infinities) are
20954 sufficient for closure of the arithmetic.
20955 </small>
20958 <p><!--para 1 -->
20959 C operators and functions provide IEC 60559 required and recommended facilities as
20960 listed below.
20961 <ul>
20962 <li> The +, -, *, and / operators provide the IEC 60559 add, subtract, multiply, and
20963 divide operations.
20964 <li> The sqrt functions in <a href="#7.12"><math.h></a> provide the IEC 60559 square root operation.
20965 <li> The remainder functions in <a href="#7.12"><math.h></a> provide the IEC 60559 remainder
20966 operation. The remquo functions in <a href="#7.12"><math.h></a> provide the same operation but
20967 with additional information.
20968 <li> The rint functions in <a href="#7.12"><math.h></a> provide the IEC 60559 operation that rounds a
20969 floating-point number to an integer value (in the same precision). The nearbyint
20970 functions in <a href="#7.12"><math.h></a> provide the nearbyinteger function recommended in the
20971 Appendix to ANSI/IEEE 854.
20972 <li> The conversions for floating types provide the IEC 60559 conversions between
20973 floating-point precisions.
20974 <li> The conversions from integer to floating types provide the IEC 60559 conversions
20975 from integer to floating point.
20976 <li> The conversions from floating to integer types provide IEC 60559-like conversions
20977 but always round toward zero.
20978 <li> The lrint and llrint functions in <a href="#7.12"><math.h></a> provide the IEC 60559
20979 conversions, which honor the directed rounding mode, from floating point to the
20980 long int and long long int integer formats. The lrint and llrint
20981 functions can be used to implement IEC 60559 conversions from floating to other
20982 integer formats.
20983 <li> The translation time conversion of floating constants and the strtod, strtof,
20984 strtold, fprintf, fscanf, and related library functions in <a href="#7.20"><stdlib.h></a>,
20985 <a href="#7.19"><stdio.h></a>, and <a href="#7.24"><wchar.h></a> provide IEC 60559 binary-decimal conversions. The
20986 strtold function in <a href="#7.20"><stdlib.h></a> provides the conv function recommended in the
20987 Appendix to ANSI/IEEE 854.
20989 <!--page 458 -->
20990 <li> The relational and equality operators provide IEC 60559 comparisons. IEC 60559
20991 identifies a need for additional comparison predicates to facilitate writing code that
20992 accounts for NaNs. The comparison macros (isgreater, isgreaterequal,
20994 supplement the language operators to address this need. The islessgreater and
20995 isunordered macros provide respectively a quiet version of the <> predicate and
20996 the unordered predicate recommended in the Appendix to IEC 60559.
20997 <li> The feclearexcept, feraiseexcept, and fetestexcept functions in
20998 <a href="#7.6"><fenv.h></a> provide the facility to test and alter the IEC 60559 floating-point
20999 exception status flags. The fegetexceptflag and fesetexceptflag
21000 functions in <a href="#7.6"><fenv.h></a> provide the facility to save and restore all five status flags at
21001 one time. These functions are used in conjunction with the type fexcept_t and the
21002 floating-point exception macros (FE_INEXACT, FE_DIVBYZERO,
21004 <li> The fegetround and fesetround functions in <a href="#7.6"><fenv.h></a> provide the facility
21005 to select among the IEC 60559 directed rounding modes represented by the rounding
21007 FE_TOWARDZERO) and the values 0, 1, 2, and 3 of FLT_ROUNDS are the
21008 IEC 60559 directed rounding modes.
21009 <li> The fegetenv, feholdexcept, fesetenv, and feupdateenv functions in
21010 <a href="#7.6"><fenv.h></a> provide a facility to manage the floating-point environment, comprising
21011 the IEC 60559 status flags and control modes.
21012 <li> The copysign functions in <a href="#7.12"><math.h></a> provide the copysign function
21013 recommended in the Appendix to IEC 60559.
21014 <li> The unary minus (-) operator provides the minus (-) operation recommended in the
21015 Appendix to IEC 60559.
21016 <li> The scalbn and scalbln functions in <a href="#7.12"><math.h></a> provide the scalb function
21017 recommended in the Appendix to IEC 60559.
21018 <li> The logb functions in <a href="#7.12"><math.h></a> provide the logb function recommended in the
21019 Appendix to IEC 60559, but following the newer specifications in ANSI/IEEE 854.
21020 <li> The nextafter and nexttoward functions in <a href="#7.12"><math.h></a> provide the nextafter
21021 function recommended in the Appendix to IEC 60559 (but with a minor change to
21022 better handle signed zeros).
21023 <li> The isfinite macro in <a href="#7.12"><math.h></a> provides the finite function recommended in
21024 the Appendix to IEC 60559.
21025 <li> The isnan macro in <a href="#7.12"><math.h></a> provides the isnan function recommended in the
21026 Appendix to IEC 60559.
21027 <!--page 459 -->
21028 <li> The signbit macro and the fpclassify macro in <a href="#7.12"><math.h></a>, used in
21029 conjunction with the number classification macros (FP_NAN, FP_INFINITE,
21030 FP_NORMAL, FP_SUBNORMAL, FP_ZERO), provide the facility of the class
21031 function recommended in the Appendix to IEC 60559 (except that the classification
21033 </ul>
21036 <p><!--para 1 -->
21037 If the floating value is infinite or NaN or if the integral part of the floating value exceeds
21038 the range of the integer type, then the ''invalid'' floating-point exception is raised and the
21039 resulting value is unspecified. Whether conversion of non-integer floating values whose
21040 integral part is within the range of the integer type raises the ''inexact'' floating-point
21043 <h6>footnotes</h6>
21044 <p><small><a name="note310" href="#note310">310)</a> ANSI/IEEE 854, but not IEC 60559 (ANSI/IEEE 754), directly specifies that floating-to-integer
21045 conversions raise the ''inexact'' floating-point exception for non-integer in-range values. In those
21046 cases where it matters, library functions can be used to effect such conversions with or without raising
21047 the ''inexact'' floating-point exception. See rint, lrint, llrint, and nearbyint in
21049 </small>
21052 <p><!--para 1 -->
21053 Conversion from the widest supported IEC 60559 format to decimal with
21054 DECIMAL_DIG digits and back is the identity function.<sup><a href="#note311"><b>311)</b></a></sup>
21055 <p><!--para 2 -->
21056 Conversions involving IEC 60559 formats follow all pertinent recommended practice. In
21057 particular, conversion between any supported IEC 60559 format and decimal with
21058 DECIMAL_DIG or fewer significant digits is correctly rounded (honoring the current
21059 rounding mode), which assures that conversion from the widest supported IEC 60559
21060 format to decimal with DECIMAL_DIG digits and back is the identity function.
21061 <p><!--para 3 -->
21062 Functions such as strtod that convert character sequences to floating types honor the
21063 rounding direction. Hence, if the rounding direction might be upward or downward, the
21064 implementation cannot convert a minus-signed sequence by negating the converted
21065 unsigned sequence.
21070 <!--page 460 -->
21072 <h6>footnotes</h6>
21073 <p><small><a name="note311" href="#note311">311)</a> If the minimum-width IEC 60559 extended format (64 bits of precision) is supported,
21074 DECIMAL_DIG shall be at least 21. If IEC 60559 double (53 bits of precision) is the widest
21075 IEC 60559 format supported, then DECIMAL_DIG shall be at least 17. (By contrast, LDBL_DIG and
21076 DBL_DIG are 18 and 15, respectively, for these formats.)
21077 </small>
21080 <p><!--para 1 -->
21081 A contracted expression treats infinities, NaNs, signed zeros, subnormals, and the
21082 rounding directions in a manner consistent with the basic arithmetic operations covered
21083 by IEC 60559.
21084 Recommended practice
21085 <p><!--para 2 -->
21086 A contracted expression should raise floating-point exceptions in a manner generally
21087 consistent with the basic arithmetic operations. A contracted expression should deliver
21088 the same value as its uncontracted counterpart, else should be correctly rounded (once).
21091 <p><!--para 1 -->
21092 The floating-point environment defined in <a href="#7.6"><fenv.h></a> includes the IEC 60559 floating-
21093 point exception status flags and directed-rounding control modes. It includes also
21094 IEC 60559 dynamic rounding precision and trap enablement modes, if the
21097 <h6>footnotes</h6>
21098 <p><small><a name="note312" href="#note312">312)</a> This specification does not require dynamic rounding precision nor trap enablement modes.
21099 </small>
21102 <p><!--para 1 -->
21103 IEC 60559 requires that floating-point operations implicitly raise floating-point exception
21104 status flags, and that rounding control modes can be set explicitly to affect result values of
21105 floating-point operations. When the state for the FENV_ACCESS pragma (defined in
21106 <a href="#7.6"><fenv.h></a>) is ''on'', these changes to the floating-point state are treated as side effects
21109 <h6>footnotes</h6>
21110 <p><small><a name="note313" href="#note313">313)</a> If the state for the FENV_ACCESS pragma is ''off'', the implementation is free to assume the floating-
21111 point control modes will be the default ones and the floating-point status flags will not be tested,
21113 </small>
21116 <p><!--para 1 -->
21117 During translation the IEC 60559 default modes are in effect:
21118 <ul>
21119 <li> The rounding direction mode is rounding to nearest.
21120 <li> The rounding precision mode (if supported) is set so that results are not shortened.
21121 <li> Trapping or stopping (if supported) is disabled on all floating-point exceptions.
21122 </ul>
21123 Recommended practice
21124 <p><!--para 2 -->
21125 The implementation should produce a diagnostic message for each translation-time
21130 <!--page 461 -->
21131 floating-point exception, other than ''inexact'';<sup><a href="#note314"><b>314)</b></a></sup> the implementation should then
21132 proceed with the translation of the program.
21134 <h6>footnotes</h6>
21135 <p><small><a name="note314" href="#note314">314)</a> As floating constants are converted to appropriate internal representations at translation time, their
21136 conversion is subject to default rounding modes and raises no execution-time floating-point exceptions
21137 (even where the state of the FENV_ACCESS pragma is ''on''). Library functions, for example
21138 strtod, provide execution-time conversion of numeric strings.
21139 </small>
21142 <p><!--para 1 -->
21143 At program startup the floating-point environment is initialized as prescribed by
21144 IEC 60559:
21145 <ul>
21146 <li> All floating-point exception status flags are cleared.
21147 <li> The rounding direction mode is rounding to nearest.
21148 <li> The dynamic rounding precision mode (if supported) is set so that results are not
21149 shortened.
21150 <li> Trapping or stopping (if supported) is disabled on all floating-point exceptions.
21151 </ul>
21154 <p><!--para 1 -->
21155 An arithmetic constant expression of floating type, other than one in an initializer for an
21156 object that has static storage duration, is evaluated (as if) during execution; thus, it is
21157 affected by any operative floating-point control modes and raises floating-point
21158 exceptions as required by IEC 60559 (provided the state for the FENV_ACCESS pragma
21160 <p><!--para 2 -->
21161 EXAMPLE
21162 <p><!--para 3 -->
21163 <pre>
21165 #pragma STDC FENV_ACCESS ON
21166 void f(void)
21167 {
21168 float w[] = { 0.0/0.0 }; // raises an exception
21169 static float x = 0.0/0.0; // does not raise an exception
21170 float y = 0.0/0.0; // raises an exception
21171 double z = 0.0/0.0; // raises an exception
21172 /* ... */
21173 }</pre>
21174 For the static initialization, the division is done at translation time, raising no (execution-time) floating-
21175 point exceptions. On the other hand, for the three automatic initializations the invalid division occurs at
21178 <!--page 462 -->
21179 execution time.
21182 <h6>footnotes</h6>
21183 <p><small><a name="note315" href="#note315">315)</a> Where the state for the FENV_ACCESS pragma is ''on'', results of inexact expressions like 1.0/3.0
21184 are affected by rounding modes set at execution time, and expressions such as 0.0/0.0 and
21185 1.0/0.0 generate execution-time floating-point exceptions. The programmer can achieve the
21186 efficiency of translation-time evaluation through static initialization, such as
21188 <pre>
21189 const static double one_third = 1.0/3.0;</pre>
21190 </small>
21193 <p><!--para 1 -->
21194 All computation for automatic initialization is done (as if) at execution time; thus, it is
21195 affected by any operative modes and raises floating-point exceptions as required by
21196 IEC 60559 (provided the state for the FENV_ACCESS pragma is ''on''). All computation
21197 for initialization of objects that have static storage duration is done (as if) at translation
21198 time.
21199 <p><!--para 2 -->
21200 EXAMPLE
21201 <p><!--para 3 -->
21202 <pre>
21204 #pragma STDC FENV_ACCESS ON
21205 void f(void)
21206 {
21207 float u[] = { 1.1e75 }; // raises exceptions
21208 static float v = 1.1e75; // does not raise exceptions
21209 float w = 1.1e75; // raises exceptions
21210 double x = 1.1e75; // may raise exceptions
21211 float y = 1.1e75f; // may raise exceptions
21212 long double z = 1.1e75; // does not raise exceptions
21213 /* ... */
21214 }</pre>
21215 The static initialization of v raises no (execution-time) floating-point exceptions because its computation is
21216 done at translation time. The automatic initialization of u and w require an execution-time conversion to
21217 float of the wider value 1.1e75, which raises floating-point exceptions. The automatic initializations
21218 of x and y entail execution-time conversion; however, in some expression evaluation methods, the
21219 conversions is not to a narrower format, in which case no floating-point exception is raised.<sup><a href="#note316"><b>316)</b></a></sup> The
21220 automatic initialization of z entails execution-time conversion, but not to a narrower format, so no floating-
21221 point exception is raised. Note that the conversions of the floating constants 1.1e75 and 1.1e75f to
21222 their internal representations occur at translation time in all cases.
21227 <!--page 463 -->
21229 <h6>footnotes</h6>
21230 <p><small><a name="note316" href="#note316">316)</a> Use of float_t and double_t variables increases the likelihood of translation-time computation.
21231 For example, the automatic initialization
21233 <pre>
21234 double_t x = 1.1e75;</pre>
21235 could be done at translation time, regardless of the expression evaluation method.
21236 </small>
21239 <p><!--para 1 -->
21240 Operations defined in <a href="#6.5">6.5</a> and functions and macros defined for the standard libraries
21241 change floating-point status flags and control modes just as indicated by their
21242 specifications (including conformance to IEC 60559). They do not change flags or modes
21243 (so as to be detectable by the user) in any other cases.
21244 <p><!--para 2 -->
21245 If the argument to the feraiseexcept function in <a href="#7.6"><fenv.h></a> represents IEC 60559
21246 valid coincident floating-point exceptions for atomic operations (namely ''overflow'' and
21247 ''inexact'', or ''underflow'' and ''inexact''), then ''overflow'' or ''underflow'' is raised
21248 before ''inexact''.
21251 <p><!--para 1 -->
21252 This section identifies code transformations that might subvert IEC 60559-specified
21253 behavior, and others that do not.
21256 <p><!--para 1 -->
21257 Floating-point arithmetic operations and external function calls may entail side effects
21258 which optimization shall honor, at least where the state of the FENV_ACCESS pragma is
21259 ''on''. The flags and modes in the floating-point environment may be regarded as global
21260 variables; floating-point operations (+, *, etc.) implicitly read the modes and write the
21261 flags.
21262 <p><!--para 2 -->
21263 Concern about side effects may inhibit code motion and removal of seemingly useless
21264 code. For example, in
21265 <pre>
21267 #pragma STDC FENV_ACCESS ON
21268 void f(double x)
21269 {
21270 /* ... */
21271 for (i = 0; i < n; i++) x + 1;
21272 /* ... */
21273 }</pre>
21274 x + 1 might raise floating-point exceptions, so cannot be removed. And since the loop
21275 body might not execute (maybe 0 >= n), x + 1 cannot be moved out of the loop. (Of
21276 course these optimizations are valid if the implementation can rule out the nettlesome
21277 cases.)
21278 <p><!--para 3 -->
21279 This specification does not require support for trap handlers that maintain information
21280 about the order or count of floating-point exceptions. Therefore, between function calls,
21281 floating-point exceptions need not be precise: the actual order and number of occurrences
21282 of floating-point exceptions (> 1) may vary from what the source code expresses. Thus,
21283 the preceding loop could be treated as
21284 <!--page 464 -->
21285 <pre>
21286 if (0 < n) x + 1;</pre>
21289 <p><!--para 1 -->
21290 x / 2 <-> x * 0.5 Although similar transformations involving inexact
21291 <pre>
21292 constants generally do not yield numerically equivalent
21293 expressions, if the constants are exact then such
21294 transformations can be made on IEC 60559 machines
21295 and others that round perfectly.</pre>
21296 1 * x and x / 1 -> x The expressions 1 * x, x / 1, and x are equivalent
21297 <pre>
21299 x / x -> 1.0 The expressions x / x and 1.0 are not equivalent if x
21300 <pre>
21301 can be zero, infinite, or NaN.</pre>
21302 x - y <-> x + (-y) The expressions x - y, x + (-y), and (-y) + x
21303 <pre>
21304 are equivalent (on IEC 60559 machines, among others).</pre>
21305 x - y <-> -(y - x) The expressions x - y and -(y - x) are not
21306 <pre>
21307 equivalent because 1 - 1 is +0 but -(1 - 1) is -0 (in the
21309 x - x -> 0.0 The expressions x - x and 0.0 are not equivalent if
21310 <pre>
21311 x is a NaN or infinite.</pre>
21312 0 * x -> 0.0 The expressions 0 * x and 0.0 are not equivalent if
21313 <pre>
21314 x is a NaN, infinite, or -0.</pre>
21315 x + 0->x The expressions x + 0 and x are not equivalent if x is
21316 <pre>
21317 -0, because (-0) + (+0) yields +0 (in the default
21318 rounding direction), not -0.</pre>
21319 x - 0->x (+0) - (+0) yields -0 when rounding is downward
21320 <pre>
21321 (toward -(inf)), but +0 otherwise, and (-0) - (+0) always
21322 yields -0; so, if the state of the FENV_ACCESS pragma
21323 is ''off'', promising default rounding, then the
21324 implementation can replace x - 0 by x, even if x</pre>
21327 <!--page 465 -->
21328 <pre>
21329 might be zero.</pre>
21330 -x <-> 0 - x The expressions -x and 0 - x are not equivalent if x
21331 <pre>
21332 is +0, because -(+0) yields -0, but 0 - (+0) yields +0
21333 (unless rounding is downward).</pre>
21335 <h6>footnotes</h6>
21336 <p><small><a name="note317" href="#note317">317)</a> Strict support for signaling NaNs -- not required by this specification -- would invalidate these and
21337 other transformations that remove arithmetic operators.
21338 </small>
21339 <p><small><a name="note318" href="#note318">318)</a> IEC 60559 prescribes a signed zero to preserve mathematical identities across certain discontinuities.
21340 Examples include:
21342 <pre>
21343 1/(1/ (+-) (inf)) is (+-) (inf)</pre>
21344 and
21346 <pre>
21347 conj(csqrt(z)) is csqrt(conj(z)),</pre>
21348 for complex z.
21349 </small>
21352 <p><!--para 1 -->
21353 x != x -> false The statement x != x is true if x is a NaN.
21354 x == x -> true The statement x == x is false if x is a NaN.
21355 x < y -> isless(x,y) (and similarly for <=, >, >=) Though numerically
21356 <pre>
21357 equal, these expressions are not equivalent because of
21358 side effects when x or y is a NaN and the state of the
21359 FENV_ACCESS pragma is ''on''. This transformation,
21360 which would be desirable if extra code were required to
21361 cause the ''invalid'' floating-point exception for
21362 unordered cases, could be performed provided the state
21363 of the FENV_ACCESS pragma is ''off''.</pre>
21364 The sense of relational operators shall be maintained. This includes handling unordered
21365 cases as expressed by the source code.
21366 <p><!--para 2 -->
21367 EXAMPLE
21368 <pre>
21369 // calls g and raises ''invalid'' if a and b are unordered
21370 if (a < b)
21371 f();
21372 else
21373 g();</pre>
21374 is not equivalent to
21375 <pre>
21376 // calls f and raises ''invalid'' if a and b are unordered
21377 if (a >= b)
21378 g();
21379 else
21380 f();</pre>
21381 nor to
21382 <pre>
21383 // calls f without raising ''invalid'' if a and b are unordered
21384 if (isgreaterequal(a,b))
21385 g();
21386 else
21387 f();</pre>
21388 nor, unless the state of the FENV_ACCESS pragma is ''off'', to
21389 <!--page 466 -->
21390 <pre>
21391 // calls g without raising ''invalid'' if a and b are unordered
21392 if (isless(a,b))
21393 f();
21394 else
21395 g();</pre>
21396 but is equivalent to
21397 <pre>
21398 if (!(a < b))
21399 g();
21400 else
21401 f();</pre>
21405 <p><!--para 1 -->
21406 The implementation shall honor floating-point exceptions raised by execution-time
21407 constant arithmetic wherever the state of the FENV_ACCESS pragma is ''on''. (See <a href="#F.7.4">F.7.4</a>
21408 and <a href="#F.7.5">F.7.5</a>.) An operation on constants that raises no floating-point exception can be
21409 folded during translation, except, if the state of the FENV_ACCESS pragma is ''on'', a
21410 further check is required to assure that changing the rounding direction to downward does
21411 not alter the sign of the result,<sup><a href="#note319"><b>319)</b></a></sup> and implementations that support dynamic rounding
21412 precision modes shall assure further that the result of the operation raises no floating-
21413 point exception when converted to the semantic type of the operation.
21415 <h6>footnotes</h6>
21416 <p><small><a name="note319" href="#note319">319)</a> 0 - 0 yields -0 instead of +0 just when the rounding direction is downward.
21417 </small>
21420 <p><!--para 1 -->
21421 This subclause contains specifications of <a href="#7.12"><math.h></a> facilities that are particularly suited
21422 for IEC 60559 implementations.
21423 <p><!--para 2 -->
21424 The Standard C macro HUGE_VAL and its float and long double analogs,
21425 HUGE_VALF and HUGE_VALL, expand to expressions whose values are positive
21426 infinities.
21427 <p><!--para 3 -->
21428 Special cases for functions in <a href="#7.12"><math.h></a> are covered directly or indirectly by
21429 IEC 60559. The functions that IEC 60559 specifies directly are identified in <a href="#F.3">F.3</a>. The
21430 other functions in <a href="#7.12"><math.h></a> treat infinities, NaNs, signed zeros, subnormals, and
21431 (provided the state of the FENV_ACCESS pragma is ''on'') the floating-point status flags
21432 in a manner consistent with the basic arithmetic operations covered by IEC 60559.
21433 <p><!--para 4 -->
21434 The expression math_errhandling & MATH_ERREXCEPT shall evaluate to a
21435 nonzero value.
21436 <p><!--para 5 -->
21437 The ''invalid'' and ''divide-by-zero'' floating-point exceptions are raised as specified in
21438 subsequent subclauses of this annex.
21439 <p><!--para 6 -->
21440 The ''overflow'' floating-point exception is raised whenever an infinity -- or, because of
21441 rounding direction, a maximal-magnitude finite number -- is returned in lieu of a value
21444 <!--page 467 -->
21445 whose magnitude is too large.
21446 <p><!--para 7 -->
21447 The ''underflow'' floating-point exception is raised whenever a result is tiny (essentially
21449 <p><!--para 8 -->
21450 Whether or when library functions raise the ''inexact'' floating-point exception is
21451 unspecified, unless explicitly specified otherwise.
21452 <p><!--para 9 -->
21453 Whether or when library functions raise an undeserved ''underflow'' floating-point
21454 exception is unspecified.<sup><a href="#note321"><b>321)</b></a></sup> Otherwise, as implied by <a href="#F.7.6">F.7.6</a>, the <a href="#7.12"><math.h></a> functions do
21455 not raise spurious floating-point exceptions (detectable by the user), other than the
21456 ''inexact'' floating-point exception.
21457 <p><!--para 10 -->
21458 Whether the functions honor the rounding direction mode is implementation-defined,
21459 unless explicitly specified otherwise.
21460 <p><!--para 11 -->
21461 Functions with a NaN argument return a NaN result and raise no floating-point exception,
21462 except where stated otherwise.
21463 <p><!--para 12 -->
21464 The specifications in the following subclauses append to the definitions in <a href="#7.12"><math.h></a>.
21465 For families of functions, the specifications apply to all of the functions even though only
21466 the principal function is shown. Unless otherwise specified, where the symbol ''(+-)''
21467 occurs in both an argument and the result, the result has the same sign as the argument.
21468 Recommended practice
21469 <p><!--para 13 -->
21470 If a function with one or more NaN arguments returns a NaN result, the result should be
21471 the same as one of the NaN arguments (after possible type conversion), except perhaps
21472 for the sign.
21474 <h6>footnotes</h6>
21475 <p><small><a name="note320" href="#note320">320)</a> IEC 60559 allows different definitions of underflow. They all result in the same values, but differ on
21476 when the floating-point exception is raised.
21477 </small>
21478 <p><small><a name="note321" href="#note321">321)</a> It is intended that undeserved ''underflow'' and ''inexact'' floating-point exceptions are raised only if
21479 avoiding them would be too costly.
21480 </small>
21485 <p><!--para 1 -->
21486 <ul>
21487 <li> acos(1) returns +0.
21488 <li> acos(x) returns a NaN and raises the ''invalid'' floating-point exception for
21489 | x | > 1.
21494 <!--page 468 -->
21495 </ul>
21498 <p><!--para 1 -->
21499 <ul>
21500 <li> asin((+-)0) returns (+-)0.
21501 <li> asin(x) returns a NaN and raises the ''invalid'' floating-point exception for
21502 | x | > 1.
21503 </ul>
21506 <p><!--para 1 -->
21507 <ul>
21508 <li> atan((+-)0) returns (+-)0.
21509 <li> atan((+-)(inf)) returns (+-)pi /2.
21510 </ul>
21513 <p><!--para 1 -->
21514 <ul>
21516 <li> atan2((+-)0, +0) returns (+-)0.
21517 <li> atan2((+-)0, x) returns (+-)pi for x < 0.
21518 <li> atan2((+-)0, x) returns (+-)0 for x > 0.
21519 <li> atan2(y, (+-)0) returns -pi /2 for y < 0.
21520 <li> atan2(y, (+-)0) returns pi /2 for y > 0.
21521 <li> atan2((+-)y, -(inf)) returns (+-)pi for finite y > 0.
21522 <li> atan2((+-)y, +(inf)) returns (+-)0 for finite y > 0.
21523 <li> atan2((+-)(inf), x) returns (+-)pi /2 for finite x.
21524 <li> atan2((+-)(inf), -(inf)) returns (+-)3pi /4.
21525 <li> atan2((+-)(inf), +(inf)) returns (+-)pi /4.
21526 </ul>
21528 <h6>footnotes</h6>
21529 <p><small><a name="note322" href="#note322">322)</a> atan2(0, 0) does not raise the ''invalid'' floating-point exception, nor does atan2( y , 0) raise
21530 the ''divide-by-zero'' floating-point exception.
21531 </small>
21534 <p><!--para 1 -->
21535 <ul>
21536 <li> cos((+-)0) returns 1.
21537 <li> cos((+-)(inf)) returns a NaN and raises the ''invalid'' floating-point exception.
21538 </ul>
21541 <p><!--para 1 -->
21542 <ul>
21543 <li> sin((+-)0) returns (+-)0.
21544 <li> sin((+-)(inf)) returns a NaN and raises the ''invalid'' floating-point exception.
21549 <!--page 469 -->
21550 </ul>
21553 <p><!--para 1 -->
21554 <ul>
21555 <li> tan((+-)0) returns (+-)0.
21556 <li> tan((+-)(inf)) returns a NaN and raises the ''invalid'' floating-point exception.
21557 </ul>
21562 <p><!--para 1 -->
21563 <ul>
21564 <li> acosh(1) returns +0.
21565 <li> acosh(x) returns a NaN and raises the ''invalid'' floating-point exception for x < 1.
21566 <li> acosh(+(inf)) returns +(inf).
21567 </ul>
21570 <p><!--para 1 -->
21571 <ul>
21572 <li> asinh((+-)0) returns (+-)0.
21573 <li> asinh((+-)(inf)) returns (+-)(inf).
21574 </ul>
21577 <p><!--para 1 -->
21578 <ul>
21579 <li> atanh((+-)0) returns (+-)0.
21580 <li> atanh((+-)1) returns (+-)(inf) and raises the ''divide-by-zero'' floating-point exception.
21581 <li> atanh(x) returns a NaN and raises the ''invalid'' floating-point exception for
21582 | x | > 1.
21583 </ul>
21586 <p><!--para 1 -->
21587 <ul>
21588 <li> cosh((+-)0) returns 1.
21589 <li> cosh((+-)(inf)) returns +(inf).
21590 </ul>
21593 <p><!--para 1 -->
21594 <ul>
21595 <li> sinh((+-)0) returns (+-)0.
21596 <li> sinh((+-)(inf)) returns (+-)(inf).
21597 </ul>
21600 <p><!--para 1 -->
21601 <ul>
21602 <li> tanh((+-)0) returns (+-)0.
21603 <li> tanh((+-)(inf)) returns (+-)1.
21604 <!--page 470 -->
21605 </ul>
21610 <p><!--para 1 -->
21611 <ul>
21612 <li> exp((+-)0) returns 1.
21613 <li> exp(-(inf)) returns +0.
21614 <li> exp(+(inf)) returns +(inf).
21615 </ul>
21618 <p><!--para 1 -->
21619 <ul>
21620 <li> exp2((+-)0) returns 1.
21621 <li> exp2(-(inf)) returns +0.
21622 <li> exp2(+(inf)) returns +(inf).
21623 </ul>
21626 <p><!--para 1 -->
21627 <ul>
21628 <li> expm1((+-)0) returns (+-)0.
21629 <li> expm1(-(inf)) returns -1.
21630 <li> expm1(+(inf)) returns +(inf).
21631 </ul>
21634 <p><!--para 1 -->
21635 <ul>
21636 <li> frexp((+-)0, exp) returns (+-)0, and stores 0 in the object pointed to by exp.
21637 <li> frexp((+-)(inf), exp) returns (+-)(inf), and stores an unspecified value in the object
21638 pointed to by exp.
21639 <li> frexp(NaN, exp) stores an unspecified value in the object pointed to by exp
21640 (and returns a NaN).
21641 </ul>
21642 <p><!--para 2 -->
21643 frexp raises no floating-point exceptions.
21644 <p><!--para 3 -->
21645 On a binary system, the body of the frexp function might be
21646 <pre>
21647 {
21648 *exp = (value == 0) ? 0 : (int)(1 + logb(value));
21649 return scalbn(value, -(*exp));
21650 }</pre>
21653 <p><!--para 1 -->
21654 If the correct result is outside the range of the return type, the numeric result is
21655 unspecified and the ''invalid'' floating-point exception is raised.
21656 <!--page 471 -->
21659 <p><!--para 1 -->
21660 On a binary system, ldexp(x, exp) is equivalent to scalbn(x, exp).
21663 <p><!--para 1 -->
21664 <ul>
21665 <li> log((+-)0) returns -(inf) and raises the ''divide-by-zero'' floating-point exception.
21666 <li> log(1) returns +0.
21667 <li> log(x) returns a NaN and raises the ''invalid'' floating-point exception for x < 0.
21668 <li> log(+(inf)) returns +(inf).
21669 </ul>
21672 <p><!--para 1 -->
21673 <ul>
21674 <li> log10((+-)0) returns -(inf) and raises the ''divide-by-zero'' floating-point exception.
21675 <li> log10(1) returns +0.
21676 <li> log10(x) returns a NaN and raises the ''invalid'' floating-point exception for x < 0.
21677 <li> log10(+(inf)) returns +(inf).
21678 </ul>
21681 <p><!--para 1 -->
21682 <ul>
21683 <li> log1p((+-)0) returns (+-)0.
21684 <li> log1p(-1) returns -(inf) and raises the ''divide-by-zero'' floating-point exception.
21685 <li> log1p(x) returns a NaN and raises the ''invalid'' floating-point exception for
21686 x < -1.
21687 <li> log1p(+(inf)) returns +(inf).
21688 </ul>
21691 <p><!--para 1 -->
21692 <ul>
21693 <li> log2((+-)0) returns -(inf) and raises the ''divide-by-zero'' floating-point exception.
21694 <li> log2(1) returns +0.
21695 <li> log2(x) returns a NaN and raises the ''invalid'' floating-point exception for x < 0.
21696 <li> log2(+(inf)) returns +(inf).
21697 </ul>
21700 <p><!--para 1 -->
21701 <ul>
21702 <li> logb((+-)0) returns -(inf) and raises the ''divide-by-zero'' floating-point exception.
21703 <li> logb((+-)(inf)) returns +(inf).
21704 <!--page 472 -->
21705 </ul>
21708 <p><!--para 1 -->
21709 <ul>
21710 <li> modf((+-)x, iptr) returns a result with the same sign as x.
21711 <li> modf((+-)(inf), iptr) returns (+-)0 and stores (+-)(inf) in the object pointed to by iptr.
21712 <li> modf(NaN, iptr) stores a NaN in the object pointed to by iptr (and returns a
21713 NaN).
21714 </ul>
21715 <p><!--para 2 -->
21716 modf behaves as though implemented by
21717 <pre>
21720 #pragma STDC FENV_ACCESS ON
21721 double modf(double value, double *iptr)
21722 {
21723 int save_round = fegetround();
21724 fesetround(FE_TOWARDZERO);
21725 *iptr = nearbyint(value);
21726 fesetround(save_round);
21727 return copysign(
21728 isinf(value) ? 0.0 :
21729 value - (*iptr), value);
21730 }</pre>
21733 <p><!--para 1 -->
21734 <ul>
21735 <li> scalbn((+-)0, n) returns (+-)0.
21736 <li> scalbn(x, 0) returns x.
21737 <li> scalbn((+-)(inf), n) returns (+-)(inf).
21738 </ul>
21743 <p><!--para 1 -->
21744 <ul>
21745 <li> cbrt((+-)0) returns (+-)0.
21746 <li> cbrt((+-)(inf)) returns (+-)(inf).
21747 </ul>
21750 <p><!--para 1 -->
21751 <ul>
21752 <li> fabs((+-)0) returns +0.
21753 <li> fabs((+-)(inf)) returns +(inf).
21754 <!--page 473 -->
21755 </ul>
21758 <p><!--para 1 -->
21759 <ul>
21760 <li> hypot(x, y), hypot(y, x), and hypot(x, -y) are equivalent.
21761 <li> hypot(x, (+-)0) is equivalent to fabs(x).
21762 <li> hypot((+-)(inf), y) returns +(inf), even if y is a NaN.
21763 </ul>
21766 <p><!--para 1 -->
21767 <ul>
21768 <li> pow((+-)0, y) returns (+-)(inf) and raises the ''divide-by-zero'' floating-point exception
21769 for y an odd integer < 0.
21770 <li> pow((+-)0, y) returns +(inf) and raises the ''divide-by-zero'' floating-point exception
21771 for y < 0 and not an odd integer.
21772 <li> pow((+-)0, y) returns (+-)0 for y an odd integer > 0.
21773 <li> pow((+-)0, y) returns +0 for y > 0 and not an odd integer.
21774 <li> pow(-1, (+-)(inf)) returns 1.
21775 <li> pow(+1, y) returns 1 for any y, even a NaN.
21776 <li> pow(x, (+-)0) returns 1 for any x, even a NaN.
21777 <li> pow(x, y) returns a NaN and raises the ''invalid'' floating-point exception for
21778 finite x < 0 and finite non-integer y.
21779 <li> pow(x, -(inf)) returns +(inf) for | x | < 1.
21780 <li> pow(x, -(inf)) returns +0 for | x | > 1.
21781 <li> pow(x, +(inf)) returns +0 for | x | < 1.
21782 <li> pow(x, +(inf)) returns +(inf) for | x | > 1.
21783 <li> pow(-(inf), y) returns -0 for y an odd integer < 0.
21784 <li> pow(-(inf), y) returns +0 for y < 0 and not an odd integer.
21785 <li> pow(-(inf), y) returns -(inf) for y an odd integer > 0.
21786 <li> pow(-(inf), y) returns +(inf) for y > 0 and not an odd integer.
21787 <li> pow(+(inf), y) returns +0 for y < 0.
21788 <li> pow(+(inf), y) returns +(inf) for y > 0.
21789 <!--page 474 -->
21790 </ul>
21793 <p><!--para 1 -->
21794 sqrt is fully specified as a basic arithmetic operation in IEC 60559.
21799 <p><!--para 1 -->
21800 <ul>
21801 <li> erf((+-)0) returns (+-)0.
21802 <li> erf((+-)(inf)) returns (+-)1.
21803 </ul>
21806 <p><!--para 1 -->
21807 <ul>
21808 <li> erfc(-(inf)) returns 2.
21809 <li> erfc(+(inf)) returns +0.
21810 </ul>
21813 <p><!--para 1 -->
21814 <ul>
21815 <li> lgamma(1) returns +0.
21816 <li> lgamma(2) returns +0.
21817 <li> lgamma(x) returns +(inf) and raises the ''divide-by-zero'' floating-point exception for
21818 x a negative integer or zero.
21819 <li> lgamma(-(inf)) returns +(inf).
21820 <li> lgamma(+(inf)) returns +(inf).
21821 </ul>
21824 <p><!--para 1 -->
21825 <ul>
21826 <li> tgamma((+-)0) returns (+-)(inf) and raises the ''divide-by-zero'' floating-point exception.
21827 <li> tgamma(x) returns a NaN and raises the ''invalid'' floating-point exception for x a
21828 negative integer.
21829 <li> tgamma(-(inf)) returns a NaN and raises the ''invalid'' floating-point exception.
21830 <li> tgamma(+(inf)) returns +(inf).
21831 </ul>
21836 <p><!--para 1 -->
21837 <ul>
21838 <li> ceil((+-)0) returns (+-)0.
21839 <li> ceil((+-)(inf)) returns (+-)(inf).
21840 </ul>
21841 <p><!--para 2 -->
21842 The double version of ceil behaves as though implemented by
21843 <!--page 475 -->
21844 <pre>
21847 #pragma STDC FENV_ACCESS ON
21848 double ceil(double x)
21849 {
21850 double result;
21851 int save_round = fegetround();
21852 fesetround(FE_UPWARD);
21853 result = rint(x); // or nearbyint instead of rint
21854 fesetround(save_round);
21855 return result;
21856 }</pre>
21859 <p><!--para 1 -->
21860 <ul>
21861 <li> floor((+-)0) returns (+-)0.
21862 <li> floor((+-)(inf)) returns (+-)(inf).
21863 </ul>
21864 <p><!--para 2 -->
21868 <p><!--para 1 -->
21869 The nearbyint functions use IEC 60559 rounding according to the current rounding
21870 direction. They do not raise the ''inexact'' floating-point exception if the result differs in
21871 value from the argument.
21872 <ul>
21873 <li> nearbyint((+-)0) returns (+-)0 (for all rounding directions).
21874 <li> nearbyint((+-)(inf)) returns (+-)(inf) (for all rounding directions).
21875 </ul>
21878 <p><!--para 1 -->
21879 The rint functions differ from the nearbyint functions only in that they do raise the
21880 ''inexact'' floating-point exception if the result differs in value from the argument.
21883 <p><!--para 1 -->
21884 The lrint and llrint functions provide floating-to-integer conversion as prescribed
21885 by IEC 60559. They round according to the current rounding direction. If the rounded
21886 value is outside the range of the return type, the numeric result is unspecified and the
21887 ''invalid'' floating-point exception is raised. When they raise no other floating-point
21888 exception and the result differs from the argument, they raise the ''inexact'' floating-point
21889 exception.
21890 <!--page 476 -->
21893 <p><!--para 1 -->
21894 <ul>
21895 <li> round((+-)0) returns (+-)0.
21896 <li> round((+-)(inf)) returns (+-)(inf).
21897 </ul>
21898 <p><!--para 2 -->
21899 The double version of round behaves as though implemented by
21900 <pre>
21903 #pragma STDC FENV_ACCESS ON
21904 double round(double x)
21905 {
21906 double result;
21907 fenv_t save_env;
21908 feholdexcept(&save_env);
21909 result = rint(x);
21910 if (fetestexcept(FE_INEXACT)) {
21911 fesetround(FE_TOWARDZERO);
21912 result = rint(copysign(0.5 + fabs(x), x));
21913 }
21914 feupdateenv(&save_env);
21915 return result;
21916 }</pre>
21917 The round functions may, but are not required to, raise the ''inexact'' floating-point
21918 exception for non-integer numeric arguments, as this implementation does.
21921 <p><!--para 1 -->
21922 The lround and llround functions differ from the lrint and llrint functions
21923 with the default rounding direction just in that the lround and llround functions
21924 round halfway cases away from zero and need not raise the ''inexact'' floating-point
21925 exception for non-integer arguments that round to within the range of the return type.
21928 <p><!--para 1 -->
21929 The trunc functions use IEC 60559 rounding toward zero (regardless of the current
21930 rounding direction).
21931 <ul>
21932 <li> trunc((+-)0) returns (+-)0.
21933 <li> trunc((+-)(inf)) returns (+-)(inf).
21934 <!--page 477 -->
21935 </ul>
21940 <p><!--para 1 -->
21941 <ul>
21942 <li> fmod((+-)0, y) returns (+-)0 for y not zero.
21943 <li> fmod(x, y) returns a NaN and raises the ''invalid'' floating-point exception for x
21944 infinite or y zero.
21945 <li> fmod(x, (+-)(inf)) returns x for x not infinite.
21946 </ul>
21947 <p><!--para 2 -->
21948 The double version of fmod behaves as though implemented by
21949 <pre>
21952 #pragma STDC FENV_ACCESS ON
21953 double fmod(double x, double y)
21954 {
21955 double result;
21956 result = remainder(fabs(x), (y = fabs(y)));
21957 if (signbit(result)) result += y;
21958 return copysign(result, x);
21959 }</pre>
21962 <p><!--para 1 -->
21963 The remainder functions are fully specified as a basic arithmetic operation in
21964 IEC 60559.
21967 <p><!--para 1 -->
21968 The remquo functions follow the specifications for the remainder functions. They
21969 have no further specifications special to IEC 60559 implementations.
21974 <p><!--para 1 -->
21975 copysign is specified in the Appendix to IEC 60559.
21978 <p><!--para 1 -->
21979 All IEC 60559 implementations support quiet NaNs, in all floating formats.
21980 <!--page 478 -->
21983 <p><!--para 1 -->
21984 <ul>
21985 <li> nextafter(x, y) raises the ''overflow'' and ''inexact'' floating-point exceptions
21986 for x finite and the function value infinite.
21987 <li> nextafter(x, y) raises the ''underflow'' and ''inexact'' floating-point
21988 exceptions for the function value subnormal or zero and x != y.
21989 </ul>
21992 <p><!--para 1 -->
21993 No additional requirements beyond those on nextafter.
21995 <h4><a name="F.9.9" href="#F.9.9">F.9.9 Maximum, minimum, and positive difference functions</a></h4>
21998 <p><!--para 1 -->
21999 No additional requirements.
22002 <p><!--para 1 -->
22003 If just one argument is a NaN, the fmax functions return the other argument (if both
22004 arguments are NaNs, the functions return a NaN).
22005 <p><!--para 2 -->
22007 <pre>
22008 { return (isgreaterequal(x, y) ||
22009 isnan(y)) ? x : y; }</pre>
22011 <h6>footnotes</h6>
22012 <p><small><a name="note323" href="#note323">323)</a> Ideally, fmax would be sensitive to the sign of zero, for example fmax(-0.0, +0.0) would
22013 return +0; however, implementation in software might be impractical.
22014 </small>
22017 <p><!--para 1 -->
22023 <p><!--para 1 -->
22024 <ul>
22025 <li> fma(x, y, z) computes xy + z, correctly rounded once.
22026 <li> fma(x, y, z) returns a NaN and optionally raises the ''invalid'' floating-point
22027 exception if one of x and y is infinite, the other is zero, and z is a NaN.
22028 <li> fma(x, y, z) returns a NaN and raises the ''invalid'' floating-point exception if
22029 one of x and y is infinite, the other is zero, and z is not a NaN.
22030 <li> fma(x, y, z) returns a NaN and raises the ''invalid'' floating-point exception if x
22031 times y is an exact infinity and z is also an infinity but with the opposite sign.
22036 <!--page 479 -->
22037 </ul>
22040 <pre>
22041 (informative)
22042 IEC 60559-compatible complex arithmetic</pre>
22045 <p><!--para 1 -->
22046 This annex supplements <a href="#F">annex F</a> to specify complex arithmetic for compatibility with
22047 IEC 60559 real floating-point arithmetic. Although these specifications have been
22048 carefully designed, there is little existing practice to validate the design decisions.
22049 Therefore, these specifications are not normative, but should be viewed more as
22050 recommended practice. An implementation that defines
22051 __STDC_IEC_559_COMPLEX__ should conform to the specifications in this annex.
22054 <p><!--para 1 -->
22055 There is a new keyword _Imaginary, which is used to specify imaginary types. It is
22056 used as a type specifier within declaration specifiers in the same way as _Complex is
22057 (thus, _Imaginary float is a valid type name).
22058 <p><!--para 2 -->
22059 There are three imaginary types, designated as float _Imaginary, double
22060 _Imaginary, and long double _Imaginary. The imaginary types (along with
22061 the real floating and complex types) are floating types.
22062 <p><!--para 3 -->
22063 For imaginary types, the corresponding real type is given by deleting the keyword
22064 _Imaginary from the type name.
22065 <p><!--para 4 -->
22066 Each imaginary type has the same representation and alignment requirements as the
22067 corresponding real type. The value of an object of imaginary type is the value of the real
22068 representation times the imaginary unit.
22069 <p><!--para 5 -->
22070 The imaginary type domain comprises the imaginary types.
22073 <p><!--para 1 -->
22074 A complex or imaginary value with at least one infinite part is regarded as an infinity
22075 (even if its other part is a NaN). A complex or imaginary value is a finite number if each
22076 of its parts is a finite number (neither infinite nor NaN). A complex or imaginary value is
22077 a zero if each of its parts is a zero.
22078 <!--page 480 -->
22083 <p><!--para 1 -->
22084 Conversions among imaginary types follow rules analogous to those for real floating
22085 types.
22088 <p><!--para 1 -->
22089 When a value of imaginary type is converted to a real type other than _Bool,<sup><a href="#note324"><b>324)</b></a></sup> the
22090 result is a positive zero.
22091 <p><!--para 2 -->
22092 When a value of real type is converted to an imaginary type, the result is a positive
22093 imaginary zero.
22095 <h6>footnotes</h6>
22097 </small>
22100 <p><!--para 1 -->
22101 When a value of imaginary type is converted to a complex type, the real part of the
22102 complex result value is a positive zero and the imaginary part of the complex result value
22103 is determined by the conversion rules for the corresponding real types.
22104 <p><!--para 2 -->
22105 When a value of complex type is converted to an imaginary type, the real part of the
22106 complex value is discarded and the value of the imaginary part is converted according to
22107 the conversion rules for the corresponding real types.
22110 <p><!--para 1 -->
22111 The following subclauses supplement <a href="#6.5">6.5</a> in order to specify the type of the result for an
22112 operation with an imaginary operand.
22113 <p><!--para 2 -->
22114 For most operand types, the value of the result of a binary operator with an imaginary or
22115 complex operand is completely determined, with reference to real arithmetic, by the usual
22116 mathematical formula. For some operand types, the usual mathematical formula is
22117 problematic because of its treatment of infinities and because of undue overflow or
22118 underflow; in these cases the result satisfies certain properties (specified in <a href="#G.5.1">G.5.1</a>), but is
22119 not completely determined.
22124 <!--page 481 -->
22127 <h6>Semantics</h6>
22128 <p><!--para 1 -->
22129 If one operand has real type and the other operand has imaginary type, then the result has
22130 imaginary type. If both operands have imaginary type, then the result has real type. (If
22131 either operand has complex type, then the result has complex type.)
22132 <p><!--para 2 -->
22133 If the operands are not both complex, then the result and floating-point exception
22134 behavior of the * operator is defined by the usual mathematical formula:
22135 <pre>
22136 * u iv u + iv</pre>
22138 <pre>
22139 x xu i(xv) (xu) + i(xv)</pre>
22141 <pre>
22142 iy i(yu) -yv (-yv) + i(yu)</pre>
22144 <p><!--para 3 -->
22145 <pre>
22146 x + iy (xu) + i(yu) (-yv) + i(xv)</pre>
22147 If the second operand is not complex, then the result and floating-point exception
22148 behavior of the / operator is defined by the usual mathematical formula:
22149 <pre>
22150 / u iv</pre>
22152 <pre>
22153 x x/u i(-x/v)</pre>
22155 <pre>
22156 iy i(y/u) y/v</pre>
22158 <p><!--para 4 -->
22159 <pre>
22160 x + iy (x/u) + i(y/u) (y/v) + i(-x/v)</pre>
22161 The * and / operators satisfy the following infinity properties for all real, imaginary, and
22163 <ul>
22164 <li> if one operand is an infinity and the other operand is a nonzero finite number or an
22165 infinity, then the result of the * operator is an infinity;
22166 <li> if the first operand is an infinity and the second operand is a finite number, then the
22167 result of the / operator is an infinity;
22168 <li> if the first operand is a finite number and the second operand is an infinity, then the
22169 result of the / operator is a zero;
22174 <!--page 482 -->
22175 <li> if the first operand is a nonzero finite number or an infinity and the second operand is
22176 a zero, then the result of the / operator is an infinity.
22177 </ul>
22178 <p><!--para 5 -->
22179 If both operands of the * operator are complex or if the second operand of the / operator
22180 is complex, the operator raises floating-point exceptions if appropriate for the calculation
22181 of the parts of the result, and may raise spurious floating-point exceptions.
22182 <p><!--para 6 -->
22183 EXAMPLE 1 Multiplication of double _Complex operands could be implemented as follows. Note
22185 <!--page 483 -->
22186 <p><!--para 7 -->
22187 <pre>
22190 /* Multiply z * w ... */
22191 double complex _Cmultd(double complex z, double complex w)
22192 {
22193 #pragma STDC FP_CONTRACT OFF
22194 double a, b, c, d, ac, bd, ad, bc, x, y;
22195 a = creal(z); b = cimag(z);
22196 c = creal(w); d = cimag(w);
22197 ac = a * c; bd = b * d;
22198 ad = a * d; bc = b * c;
22199 x = ac - bd; y = ad + bc;
22200 if (isnan(x) && isnan(y)) {
22201 /* Recover infinities that computed as NaN+iNaN ... */
22202 int recalc = 0;
22203 if ( isinf(a) || isinf(b) ) { // z is infinite
22205 a = copysign(isinf(a) ? 1.0 : 0.0, a);
22206 b = copysign(isinf(b) ? 1.0 : 0.0, b);
22207 if (isnan(c)) c = copysign(0.0, c);
22208 if (isnan(d)) d = copysign(0.0, d);
22209 recalc = 1;
22210 }
22211 if ( isinf(c) || isinf(d) ) { // w is infinite
22213 c = copysign(isinf(c) ? 1.0 : 0.0, c);
22214 d = copysign(isinf(d) ? 1.0 : 0.0, d);
22215 if (isnan(a)) a = copysign(0.0, a);
22216 if (isnan(b)) b = copysign(0.0, b);
22217 recalc = 1;
22218 }
22219 if (!recalc && (isinf(ac) || isinf(bd) ||
22220 isinf(ad) || isinf(bc))) {
22221 /* Recover infinities from overflow by changing NaNs to 0 ... */
22222 if (isnan(a)) a = copysign(0.0, a);
22223 if (isnan(b)) b = copysign(0.0, b);
22224 if (isnan(c)) c = copysign(0.0, c);
22225 if (isnan(d)) d = copysign(0.0, d);
22226 recalc = 1;
22227 }
22228 if (recalc) {
22229 x = INFINITY * ( a * c - b * d );
22230 y = INFINITY * ( a * d + b * c );
22231 }
22232 }
22233 return x + I * y;
22234 }</pre>
22235 This implementation achieves the required treatment of infinities at the cost of only one isnan test in
22236 ordinary (finite) cases. It is less than ideal in that undue overflow and underflow may occur.
22238 <p><!--para 8 -->
22239 EXAMPLE 2 Division of two double _Complex operands could be implemented as follows.
22240 <!--page 484 -->
22241 <p><!--para 9 -->
22242 <pre>
22245 /* Divide z / w ... */
22246 double complex _Cdivd(double complex z, double complex w)
22247 {
22248 #pragma STDC FP_CONTRACT OFF
22249 double a, b, c, d, logbw, denom, x, y;
22250 int ilogbw = 0;
22251 a = creal(z); b = cimag(z);
22252 c = creal(w); d = cimag(w);
22253 logbw = logb(fmax(fabs(c), fabs(d)));
22254 if (isfinite(logbw)) {
22255 ilogbw = (int)logbw;
22256 c = scalbn(c, -ilogbw); d = scalbn(d, -ilogbw);
22257 }
22258 denom = c * c + d * d;
22259 x = scalbn((a * c + b * d) / denom, -ilogbw);
22260 y = scalbn((b * c - a * d) / denom, -ilogbw);
22261 /* Recover infinities and zeros that computed as NaN+iNaN; */
22262 /* the only cases are nonzero/zero, infinite/finite, and finite/infinite, ... */
22263 if (isnan(x) && isnan(y)) {
22264 if ((denom == 0.0) &&
22265 (!isnan(a) || !isnan(b))) {
22266 x = copysign(INFINITY, c) * a;
22267 y = copysign(INFINITY, c) * b;
22268 }
22269 else if ((isinf(a) || isinf(b)) &&
22270 isfinite(c) && isfinite(d)) {
22271 a = copysign(isinf(a) ? 1.0 : 0.0, a);
22272 b = copysign(isinf(b) ? 1.0 : 0.0, b);
22273 x = INFINITY * ( a * c + b * d );
22274 y = INFINITY * ( b * c - a * d );
22275 }
22276 else if (isinf(logbw) &&
22277 isfinite(a) && isfinite(b)) {
22278 c = copysign(isinf(c) ? 1.0 : 0.0, c);
22279 d = copysign(isinf(d) ? 1.0 : 0.0, d);
22280 x = 0.0 * ( a * c + b * d );
22281 y = 0.0 * ( b * c - a * d );
22282 }
22283 }
22284 return x + I * y;
22285 }</pre>
22286 Scaling the denominator alleviates the main overflow and underflow problem, which is more serious than
22287 for multiplication. In the spirit of the multiplication example above, this code does not defend against
22288 overflow and underflow in the calculation of the numerator. Scaling with the scalbn function, instead of
22289 with division, provides better roundoff characteristics.
22292 <h6>footnotes</h6>
22293 <p><small><a name="note325" href="#note325">325)</a> These properties are already implied for those cases covered in the tables, but are required for all cases
22294 (at least where the state for CX_LIMITED_RANGE is ''off'').
22295 </small>
22298 <h6>Semantics</h6>
22299 <p><!--para 1 -->
22300 If both operands have imaginary type, then the result has imaginary type. (If one operand
22301 has real type and the other operand has imaginary type, or if either operand has complex
22302 type, then the result has complex type.)
22303 <p><!--para 2 -->
22304 In all cases the result and floating-point exception behavior of a + or - operator is defined
22305 by the usual mathematical formula:
22306 <pre>
22307 + or - u iv u + iv</pre>
22309 <pre>
22310 x x(+-)u x (+-) iv (x (+-) u) (+-) iv</pre>
22312 <pre>
22313 iy (+-)u + iy i(y (+-) v) (+-)u + i(y (+-) v)</pre>
22315 <pre>
22316 x + iy (x (+-) u) + iy x + i(y (+-) v) (x (+-) u) + i(y (+-) v)</pre>
22319 <p><!--para 1 -->
22320 The macros
22321 <pre>
22322 imaginary</pre>
22323 and
22324 <pre>
22325 _Imaginary_I</pre>
22326 are defined, respectively, as _Imaginary and a constant expression of type const
22327 float _Imaginary with the value of the imaginary unit. The macro
22328 <pre>
22329 I</pre>
22330 is defined to be _Imaginary_I (not _Complex_I as stated in <a href="#7.3">7.3</a>). Notwithstanding
22331 the provisions of <a href="#7.1.3">7.1.3</a>, a program may undefine and then perhaps redefine the macro
22332 imaginary.
22333 <p><!--para 2 -->
22334 This subclause contains specifications for the <a href="#7.3"><complex.h></a> functions that are
22335 particularly suited to IEC 60559 implementations. For families of functions, the
22336 specifications apply to all of the functions even though only the principal function is
22337 <!--page 485 -->
22338 shown. Unless otherwise specified, where the symbol ''(+-)'' occurs in both an argument
22339 and the result, the result has the same sign as the argument.
22340 <p><!--para 3 -->
22341 The functions are continuous onto both sides of their branch cuts, taking into account the
22342 sign of zero. For example, csqrt(-2 (+-) i0) = (+-)i(sqrt)2. ???
22343 <p><!--para 4 -->
22344 Since complex and imaginary values are composed of real values, each function may be
22345 regarded as computing real values from real values. Except as noted, the functions treat
22346 real infinities, NaNs, signed zeros, subnormals, and the floating-point exception flags in a
22347 manner consistent with the specifications for real functions in F.9.<sup><a href="#note326"><b>326)</b></a></sup>
22348 <p><!--para 5 -->
22349 The functions cimag, conj, cproj, and creal are fully specified for all
22350 implementations, including IEC 60559 ones, in <a href="#7.3.9">7.3.9</a>. These functions raise no floating-
22351 point exceptions.
22352 <p><!--para 6 -->
22353 Each of the functions cabs and carg is specified by a formula in terms of a real
22355 <p><!--para 7 -->
22356 <pre>
22357 cabs(x + iy) = hypot(x, y)
22358 carg(x + iy) = atan2(y, x)</pre>
22359 Each of the functions casin, catan, ccos, csin, and ctan is specified implicitly by
22360 a formula in terms of other complex functions (whose special cases are specified below):
22361 <p><!--para 8 -->
22362 <pre>
22363 casin(z) = -i casinh(iz)
22364 catan(z) = -i catanh(iz)
22365 ccos(z) = ccosh(iz)
22366 csin(z) = -i csinh(iz)
22367 ctan(z) = -i ctanh(iz)</pre>
22368 For the other functions, the following subclauses specify behavior for special cases,
22369 including treatment of the ''invalid'' and ''divide-by-zero'' floating-point exceptions. For
22370 families of functions, the specifications apply to all of the functions even though only the
22371 principal function is shown. For a function f satisfying f (conj(z)) = conj( f (z)), the
22372 specifications for the upper half-plane imply the specifications for the lower half-plane; if
22373 the function f is also either even, f (-z) = f (z), or odd, f (-z) = - f (z), then the
22374 specifications for the first quadrant imply the specifications for the other three quadrants.
22375 <p><!--para 9 -->
22376 In the following subclauses, cis(y) is defined as cos(y) + i sin(y).
22381 <!--page 486 -->
22383 <h6>footnotes</h6>
22384 <p><small><a name="note326" href="#note326">326)</a> As noted in <a href="#G.3">G.3</a>, a complex value with at least one infinite part is regarded as an infinity even if its
22385 other part is a NaN.
22386 </small>
22391 <p><!--para 1 -->
22392 <ul>
22393 <li> cacos(conj(z)) = conj(cacos(z)).
22394 <li> cacos((+-)0 + i0) returns pi /2 - i0.
22395 <li> cacos((+-)0 + iNaN) returns pi /2 + iNaN.
22396 <li> cacos(x + i (inf)) returns pi /2 - i (inf), for finite x.
22397 <li> cacos(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
22398 point exception, for nonzero finite x.
22399 <li> cacos(-(inf) + iy) returns pi - i (inf), for positive-signed finite y.
22400 <li> cacos(+(inf) + iy) returns +0 - i (inf), for positive-signed finite y.
22401 <li> cacos(-(inf) + i (inf)) returns 3pi /4 - i (inf).
22402 <li> cacos(+(inf) + i (inf)) returns pi /4 - i (inf).
22403 <li> cacos((+-)(inf) + iNaN) returns NaN (+-) i (inf) (where the sign of the imaginary part of the
22404 result is unspecified).
22405 <li> cacos(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
22406 point exception, for finite y.
22407 <li> cacos(NaN + i (inf)) returns NaN - i (inf).
22408 <li> cacos(NaN + iNaN) returns NaN + iNaN.
22409 </ul>
22414 <p><!--para 1 -->
22415 <ul>
22416 <li> cacosh(conj(z)) = conj(cacosh(z)).
22417 <li> cacosh((+-)0 + i0) returns +0 + ipi /2.
22418 <li> cacosh(x + i (inf)) returns +(inf) + ipi /2, for finite x.
22419 <li> cacosh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid''
22420 floating-point exception, for finite x.
22421 <li> cacosh(-(inf) + iy) returns +(inf) + ipi , for positive-signed finite y.
22422 <li> cacosh(+(inf) + iy) returns +(inf) + i0, for positive-signed finite y.
22423 <li> cacosh(-(inf) + i (inf)) returns +(inf) + i3pi /4.
22424 <li> cacosh(+(inf) + i (inf)) returns +(inf) + ipi /4.
22425 <li> cacosh((+-)(inf) + iNaN) returns +(inf) + iNaN.
22426 <!--page 487 -->
22427 <li> cacosh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid''
22428 floating-point exception, for finite y.
22429 <li> cacosh(NaN + i (inf)) returns +(inf) + iNaN.
22430 <li> cacosh(NaN + iNaN) returns NaN + iNaN.
22431 </ul>
22434 <p><!--para 1 -->
22435 <ul>
22436 <li> casinh(conj(z)) = conj(casinh(z)) and casinh is odd.
22437 <li> casinh(+0 + i0) returns 0 + i0.
22438 <li> casinh(x + i (inf)) returns +(inf) + ipi /2 for positive-signed finite x.
22439 <li> casinh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid''
22440 floating-point exception, for finite x.
22441 <li> casinh(+(inf) + iy) returns +(inf) + i0 for positive-signed finite y.
22442 <li> casinh(+(inf) + i (inf)) returns +(inf) + ipi /4.
22443 <li> casinh(+(inf) + iNaN) returns +(inf) + iNaN.
22444 <li> casinh(NaN + i0) returns NaN + i0.
22445 <li> casinh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid''
22446 floating-point exception, for finite nonzero y.
22447 <li> casinh(NaN + i (inf)) returns (+-)(inf) + iNaN (where the sign of the real part of the result
22448 is unspecified).
22449 <li> casinh(NaN + iNaN) returns NaN + iNaN.
22450 </ul>
22453 <p><!--para 1 -->
22454 <ul>
22455 <li> catanh(conj(z)) = conj(catanh(z)) and catanh is odd.
22456 <li> catanh(+0 + i0) returns +0 + i0.
22457 <li> catanh(+0 + iNaN) returns +0 + iNaN.
22458 <li> catanh(+1 + i0) returns +(inf) + i0 and raises the ''divide-by-zero'' floating-point
22459 exception.
22460 <li> catanh(x + i (inf)) returns +0 + ipi /2, for finite positive-signed x.
22461 <li> catanh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid''
22462 floating-point exception, for nonzero finite x.
22463 <li> catanh(+(inf) + iy) returns +0 + ipi /2, for finite positive-signed y.
22464 <li> catanh(+(inf) + i (inf)) returns +0 + ipi /2.
22465 <li> catanh(+(inf) + iNaN) returns +0 + iNaN.
22466 <!--page 488 -->
22467 <li> catanh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid''
22468 floating-point exception, for finite y.
22469 <li> catanh(NaN + i (inf)) returns (+-)0 + ipi /2 (where the sign of the real part of the result is
22470 unspecified).
22471 <li> catanh(NaN + iNaN) returns NaN + iNaN.
22472 </ul>
22475 <p><!--para 1 -->
22476 <ul>
22477 <li> ccosh(conj(z)) = conj(ccosh(z)) and ccosh is even.
22478 <li> ccosh(+0 + i0) returns 1 + i0.
22479 <li> ccosh(+0 + i (inf)) returns NaN (+-) i0 (where the sign of the imaginary part of the
22480 result is unspecified) and raises the ''invalid'' floating-point exception.
22481 <li> ccosh(+0 + iNaN) returns NaN (+-) i0 (where the sign of the imaginary part of the
22482 result is unspecified).
22483 <li> ccosh(x + i (inf)) returns NaN + iNaN and raises the ''invalid'' floating-point
22484 exception, for finite nonzero x.
22485 <li> ccosh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
22486 point exception, for finite nonzero x.
22487 <li> ccosh(+(inf) + i0) returns +(inf) + i0.
22488 <li> ccosh(+(inf) + iy) returns +(inf) cis(y), for finite nonzero y.
22489 <li> ccosh(+(inf) + i (inf)) returns (+-)(inf) + iNaN (where the sign of the real part of the result is
22490 unspecified) and raises the ''invalid'' floating-point exception.
22491 <li> ccosh(+(inf) + iNaN) returns +(inf) + iNaN.
22492 <li> ccosh(NaN + i0) returns NaN (+-) i0 (where the sign of the imaginary part of the
22493 result is unspecified).
22494 <li> ccosh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
22495 point exception, for all nonzero numbers y.
22496 <li> ccosh(NaN + iNaN) returns NaN + iNaN.
22497 </ul>
22500 <p><!--para 1 -->
22501 <ul>
22502 <li> csinh(conj(z)) = conj(csinh(z)) and csinh is odd.
22503 <li> csinh(+0 + i0) returns +0 + i0.
22504 <li> csinh(+0 + i (inf)) returns (+-)0 + iNaN (where the sign of the real part of the result is
22505 unspecified) and raises the ''invalid'' floating-point exception.
22506 <li> csinh(+0 + iNaN) returns (+-)0 + iNaN (where the sign of the real part of the result is
22507 unspecified).
22508 <!--page 489 -->
22509 <li> csinh(x + i (inf)) returns NaN + iNaN and raises the ''invalid'' floating-point
22510 exception, for positive finite x.
22511 <li> csinh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
22512 point exception, for finite nonzero x.
22513 <li> csinh(+(inf) + i0) returns +(inf) + i0.
22514 <li> csinh(+(inf) + iy) returns +(inf) cis(y), for positive finite y.
22515 <li> csinh(+(inf) + i (inf)) returns (+-)(inf) + iNaN (where the sign of the real part of the result is
22516 unspecified) and raises the ''invalid'' floating-point exception.
22517 <li> csinh(+(inf) + iNaN) returns (+-)(inf) + iNaN (where the sign of the real part of the result
22518 is unspecified).
22519 <li> csinh(NaN + i0) returns NaN + i0.
22520 <li> csinh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
22521 point exception, for all nonzero numbers y.
22522 <li> csinh(NaN + iNaN) returns NaN + iNaN.
22523 </ul>
22526 <p><!--para 1 -->
22527 <ul>
22528 <li> ctanh(conj(z)) = conj(ctanh(z))and ctanh is odd.
22529 <li> ctanh(+0 + i0) returns +0 + i0.
22530 <li> ctanh(x + i (inf)) returns NaN + iNaN and raises the ''invalid'' floating-point
22531 exception, for finite x.
22532 <li> ctanh(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
22533 point exception, for finite x.
22534 <li> ctanh(+(inf) + iy) returns 1 + i0 sin(2y), for positive-signed finite y.
22535 <li> ctanh(+(inf) + i (inf)) returns 1 (+-) i0 (where the sign of the imaginary part of the result
22536 is unspecified).
22537 <li> ctanh(+(inf) + iNaN) returns 1 (+-) i0 (where the sign of the imaginary part of the
22538 result is unspecified).
22539 <li> ctanh(NaN + i0) returns NaN + i0.
22540 <li> ctanh(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
22541 point exception, for all nonzero numbers y.
22542 <li> ctanh(NaN + iNaN) returns NaN + iNaN.
22543 <!--page 490 -->
22544 </ul>
22549 <p><!--para 1 -->
22550 <ul>
22551 <li> cexp(conj(z)) = conj(cexp(z)).
22552 <li> cexp((+-)0 + i0) returns 1 + i0.
22553 <li> cexp(x + i (inf)) returns NaN + iNaN and raises the ''invalid'' floating-point
22554 exception, for finite x.
22555 <li> cexp(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
22556 point exception, for finite x.
22557 <li> cexp(+(inf) + i0) returns +(inf) + i0.
22558 <li> cexp(-(inf) + iy) returns +0 cis(y), for finite y.
22559 <li> cexp(+(inf) + iy) returns +(inf) cis(y), for finite nonzero y.
22560 <li> cexp(-(inf) + i (inf)) returns (+-)0 (+-) i0 (where the signs of the real and imaginary parts of
22561 the result are unspecified).
22562 <li> cexp(+(inf) + i (inf)) returns (+-)(inf) + iNaN and raises the ''invalid'' floating-point
22563 exception (where the sign of the real part of the result is unspecified).
22564 <li> cexp(-(inf) + iNaN) returns (+-)0 (+-) i0 (where the signs of the real and imaginary parts
22565 of the result are unspecified).
22566 <li> cexp(+(inf) + iNaN) returns (+-)(inf) + iNaN (where the sign of the real part of the result
22567 is unspecified).
22568 <li> cexp(NaN + i0) returns NaN + i0.
22569 <li> cexp(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
22570 point exception, for all nonzero numbers y.
22571 <li> cexp(NaN + iNaN) returns NaN + iNaN.
22572 </ul>
22575 <p><!--para 1 -->
22576 <ul>
22577 <li> clog(conj(z)) = conj(clog(z)).
22578 <li> clog(-0 + i0) returns -(inf) + ipi and raises the ''divide-by-zero'' floating-point
22579 exception.
22580 <li> clog(+0 + i0) returns -(inf) + i0 and raises the ''divide-by-zero'' floating-point
22581 exception.
22582 <li> clog(x + i (inf)) returns +(inf) + ipi /2, for finite x.
22583 <li> clog(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
22584 point exception, for finite x.
22585 <!--page 491 -->
22586 <li> clog(-(inf) + iy) returns +(inf) + ipi , for finite positive-signed y.
22587 <li> clog(+(inf) + iy) returns +(inf) + i0, for finite positive-signed y.
22588 <li> clog(-(inf) + i (inf)) returns +(inf) + i3pi /4.
22589 <li> clog(+(inf) + i (inf)) returns +(inf) + ipi /4.
22590 <li> clog((+-)(inf) + iNaN) returns +(inf) + iNaN.
22591 <li> clog(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
22592 point exception, for finite y.
22593 <li> clog(NaN + i (inf)) returns +(inf) + iNaN.
22594 <li> clog(NaN + iNaN) returns NaN + iNaN.
22595 </ul>
22600 <p><!--para 1 -->
22601 The cpow functions raise floating-point exceptions if appropriate for the calculation of
22602 the parts of the result, and may raise spurious exceptions.<sup><a href="#note327"><b>327)</b></a></sup>
22604 <h6>footnotes</h6>
22605 <p><small><a name="note327" href="#note327">327)</a> This allows cpow( z , c ) to be implemented as cexp(c clog( z )) without precluding
22606 implementations that treat special cases more carefully.
22607 </small>
22610 <p><!--para 1 -->
22611 <ul>
22612 <li> csqrt(conj(z)) = conj(csqrt(z)).
22613 <li> csqrt((+-)0 + i0) returns +0 + i0.
22614 <li> csqrt(x + i (inf)) returns +(inf) + i (inf), for all x (including NaN).
22615 <li> csqrt(x + iNaN) returns NaN + iNaN and optionally raises the ''invalid'' floating-
22616 point exception, for finite x.
22617 <li> csqrt(-(inf) + iy) returns +0 + i (inf), for finite positive-signed y.
22618 <li> csqrt(+(inf) + iy) returns +(inf) + i0, for finite positive-signed y.
22619 <li> csqrt(-(inf) + iNaN) returns NaN (+-) i (inf) (where the sign of the imaginary part of the
22620 result is unspecified).
22621 <li> csqrt(+(inf) + iNaN) returns +(inf) + iNaN.
22622 <li> csqrt(NaN + iy) returns NaN + iNaN and optionally raises the ''invalid'' floating-
22623 point exception, for finite y.
22624 <li> csqrt(NaN + iNaN) returns NaN + iNaN.
22629 <!--page 492 -->
22630 </ul>
22633 <p><!--para 1 -->
22634 Type-generic macros that accept complex arguments also accept imaginary arguments. If
22635 an argument is imaginary, the macro expands to an expression whose type is real,
22636 imaginary, or complex, as appropriate for the particular function: if the argument is
22637 imaginary, then the types of cos, cosh, fabs, carg, cimag, and creal are real; the
22638 types of sin, tan, sinh, tanh, asin, atan, asinh, and atanh are imaginary; and
22639 the types of the others are complex.
22640 <p><!--para 2 -->
22641 Given an imaginary argument, each of the type-generic macros cos, sin, tan, cosh,
22642 sinh, tanh, asin, atan, asinh, atanh is specified by a formula in terms of real
22643 functions:
22644 <!--page 493 -->
22645 <pre>
22646 cos(iy) = cosh(y)
22647 sin(iy) = i sinh(y)
22648 tan(iy) = i tanh(y)
22649 cosh(iy) = cos(y)
22650 sinh(iy) = i sin(y)
22651 tanh(iy) = i tan(y)
22652 asin(iy) = i asinh(y)
22653 atan(iy) = i atanh(y)
22654 asinh(iy) = i asin(y)
22655 atanh(iy) = i atan(y)</pre>
22658 <pre>
22659 (informative)
22660 Language independent arithmetic</pre>
22663 <p><!--para 1 -->
22664 This annex documents the extent to which the C language supports the ISO/IEC 10967-1
22665 standard for language-independent arithmetic (LIA-1). LIA-1 is more general than
22666 IEC 60559 (<a href="#F">annex F</a>) in that it covers integer and diverse floating-point arithmetics.
22669 <p><!--para 1 -->
22670 The relevant C arithmetic types meet the requirements of LIA-1 types if an
22671 implementation adds notification of exceptional arithmetic operations and meets the 1
22672 unit in the last place (ULP) accuracy requirement (LIA-1 subclause <a href="#5.2.8">5.2.8</a>).
22675 <p><!--para 1 -->
22676 The LIA-1 data type Boolean is implemented by the C data type bool with values of
22680 <p><!--para 1 -->
22681 The signed C integer types int, long int, long long int, and the corresponding
22682 unsigned types are compatible with LIA-1. If an implementation adds support for the
22683 LIA-1 exceptional values ''integer_overflow'' and ''undefined'', then those types are
22684 LIA-1 conformant types. C's unsigned integer types are ''modulo'' in the LIA-1 sense
22685 in that overflows or out-of-bounds results silently wrap. An implementation that defines
22686 signed integer types as also being modulo need not detect integer overflow, in which case,
22687 only integer divide-by-zero need be detected.
22688 <p><!--para 2 -->
22689 The parameters for the integer data types can be accessed by the following:
22690 maxint INT_MAX, LONG_MAX, LLONG_MAX, UINT_MAX, ULONG_MAX,
22691 <pre>
22692 ULLONG_MAX</pre>
22693 minint INT_MIN, LONG_MIN, LLONG_MIN
22694 <p><!--para 3 -->
22695 The parameter ''bounded'' is always true, and is not provided. The parameter ''minint''
22696 is always 0 for the unsigned types, and is not provided for those types.
22697 <!--page 494 -->
22700 <p><!--para 1 -->
22701 The integer operations on integer types are the following:
22702 addI x + y
22703 subI x - y
22704 mulI x * y
22705 divI, divtI x / y
22706 remI, remtI x % y
22707 negI -x
22708 absI abs(x), labs(x), llabs(x)
22709 eqI x == y
22710 neqI x != y
22711 lssI x < y
22712 leqI x <= y
22713 gtrI x > y
22714 geqI x >= y
22715 where x and y are expressions of the same integer type.
22718 <p><!--para 1 -->
22719 The C floating-point types float, double, and long double are compatible with
22720 LIA-1. If an implementation adds support for the LIA-1 exceptional values
22721 ''underflow'', ''floating_overflow'', and ''"undefined'', then those types are conformant
22723 operations (see <a href="#F">annex F</a>) along with IEC 60559 status flags and traps has LIA-1
22724 conformant types.
22728 The parameters for a floating point data type can be accessed by the following:
22729 r FLT_RADIX
22730 p FLT_MANT_DIG, DBL_MANT_DIG, LDBL_MANT_DIG
22731 emax FLT_MAX_EXP, DBL_MAX_EXP, LDBL_MAX_EXP
22732 emin FLT_MIN_EXP, DBL_MIN_EXP, LDBL_MIN_EXP
22734 The derived constants for the floating point types are accessed by the following:
22735 <!--page 495 -->
22736 fmax FLT_MAX, DBL_MAX, LDBL_MAX
22737 fminN FLT_MIN, DBL_MIN, LDBL_MIN
22738 epsilon FLT_EPSILON, DBL_EPSILON, LDBL_EPSILON
22739 rnd_style FLT_ROUNDS
22743 The floating-point operations on floating-point types are the following:
22744 addF x + y
22745 subF x - y
22746 mulF x * y
22747 divF x / y
22748 negF -x
22749 absF fabsf(x), fabs(x), fabsl(x)
22751 scaleF scalbnf(x, n), scalbn(x, n), scalbnl(x, n),
22752 <pre>
22753 scalblnf(x, li), scalbln(x, li), scalblnl(x, li)</pre>
22756 eqF x == y
22757 neqF x != y
22758 lssF x < y
22759 leqF x <= y
22760 gtrF x > y
22761 geqF x >= y
22762 where x and y are expressions of the same floating point type, n is of type int, and li
22763 is of type long int.
22767 The C Standard requires all floating types to use the same radix and rounding style, so
22768 that only one identifier for each is provided to map to LIA-1.
22770 The FLT_ROUNDS parameter can be used to indicate the LIA-1 rounding styles:
22771 truncate FLT_ROUNDS == 0
22772 <!--page 496 -->
22773 nearest FLT_ROUNDS == 1
22775 provided that an implementation extends FLT_ROUNDS to cover the rounding style used
22776 in all relevant LIA-1 operations, not just addition as in C.
22780 The LIA-1 type conversions are the following type casts:
22781 cvtI' -> I (int)i, (long int)i, (long long int)i,
22782 <pre>
22783 (unsigned int)i, (unsigned long int)i,
22784 (unsigned long long int)i</pre>
22785 cvtF -> I (int)x, (long int)x, (long long int)x,
22786 <pre>
22787 (unsigned int)x, (unsigned long int)x,
22788 (unsigned long long int)x</pre>
22789 cvtI -> F (float)i, (double)i, (long double)i
22790 cvtF' -> F (float)x, (double)x, (long double)x
22792 In the above conversions from floating to integer, the use of (cast)x can be replaced with
22793 (cast)round(x), (cast)rint(x), (cast)nearbyint(x), (cast)trunc(x),
22794 (cast)ceil(x), or (cast)floor(x). In addition, C's floating-point to integer
22795 conversion functions, lrint(), llrint(), lround(), and llround(), can be
22796 used. They all meet LIA-1's requirements on floating to integer rounding for in-range
22797 values. For out-of-range values, the conversions shall silently wrap for the modulo types.
22799 The fmod() function is useful for doing silent wrapping to unsigned integer types, e.g.,
22802 to 65535.0 which can then be cast to unsigned short int. But, the
22803 remainder() function is not useful for doing silent wrapping to signed integer types,
22804 e.g., remainder( rint(x), 65536.0 ) will compute an integer value in the
22806 int.
22808 C's conversions (casts) from floating-point to floating-point can meet LIA-1
22809 requirements if an implementation uses round-to-nearest (IEC 60559 default).
22811 C's conversions (casts) from integer to floating-point can meet LIA-1 requirements if an
22812 implementation uses round-to-nearest.
22813 <!--page 497 -->
22817 Notification is the process by which a user or program is informed that an exceptional
22818 arithmetic operation has occurred. C's operations are compatible with LIA-1 in that C
22819 allows an implementation to cause a notification to occur when any arithmetic operation
22824 LIA-1 requires at least the following two alternatives for handling of notifications:
22825 setting indicators or trap-and-terminate. LIA-1 allows a third alternative: trap-and-
22826 resume.
22828 An implementation need only support a given notification alternative for the entire
22829 program. An implementation may support the ability to switch between notification
22830 alternatives during execution, but is not required to do so. An implementation can
22831 provide separate selection for each kind of notification, but this is not required.
22833 C allows an implementation to provide notification. C's SIGFPE (for traps) and
22834 FE_INVALID, FE_DIVBYZERO, FE_OVERFLOW, FE_UNDERFLOW (for indicators)
22835 can provide LIA-1 notification.
22837 C's signal handlers are compatible with LIA-1. Default handling of SIGFPE can
22838 provide trap-and-terminate behavior, except for those LIA-1 operations implemented by
22839 math library function calls. User-provided signal handlers for SIGFPE allow for trap-
22840 and-resume behavior with the same constraint.
22846 The following mapping is for floating-point types:
22847 undefined FE_INVALID, FE_DIVBYZERO
22848 floating_overflow FE_OVERFLOW
22849 underflow FE_UNDERFLOW
22851 The floating-point indicator interrogation and manipulation operations are:
22852 set_indicators feraiseexcept(i)
22853 clear_indicators feclearexcept(i)
22854 test_indicators fetestexcept(i)
22855 current_indicators fetestexcept(FE_ALL_EXCEPT)
22856 where i is an expression of type int representing a subset of the LIA-1 indicators.
22858 C allows an implementation to provide the following LIA-1 required behavior: at
22859 program termination if any indicator is set the implementation shall send an unambiguous
22860 <!--page 498 -->
22863 LIA-1 does not make the distinction between floating-point and integer for ''undefined''.
22864 This documentation makes that distinction because <a href="#7.6"><fenv.h></a> covers only the floating-
22865 point indicators.
22869 C is compatible with LIA-1's trap requirements for arithmetic operations, but not for
22870 math library functions (which are not permitted to generate any externally visible
22871 exceptional conditions). An implementation can provide an alternative of notification
22872 through termination with a ''hard-to-ignore'' message (see LIA-1 subclause <a href="#6.1.3">6.1.3</a>).
22874 LIA-1 does not require that traps be precise.
22876 C does require that SIGFPE be the signal corresponding to arithmetic exceptions, if there
22877 is any signal raised for them.
22879 C supports signal handlers for SIGFPE and allows trapping of arithmetic exceptions.
22880 When arithmetic exceptions do trap, C's signal-handler mechanism allows trap-and-
22881 terminate (either default implementation behavior or user replacement for it) or trap-and-
22882 resume, at the programmer's option.
22883 <!--page 499 -->
22887 <pre>
22888 (informative)
22889 Common warnings</pre>
22890 An implementation may generate warnings in many situations, none of which are
22891 specified as part of this International Standard. The following are a few of the more
22892 common situations.
22894 <ul>
22895 <li> A new struct or union type appears in a function prototype (<a href="#6.2.1">6.2.1</a>, <a href="#6.7.2.3">6.7.2.3</a>).
22896 <li> A block with initialization of an object that has automatic storage duration is jumped
22898 <li> An implicit narrowing conversion is encountered, such as the assignment of a long
22899 int or a double to an int, or a pointer to void to a pointer to any type other than
22901 <li> A hexadecimal floating constant cannot be represented exactly in its evaluation format
22903 <li> An integer character constant includes more than one character or a wide character
22906 <li> An ''unordered'' binary operator (not comma, &&, or ||) contains a side effect to an
22907 lvalue in one operand, and a side effect to, or an access to the value of, the identical
22909 <li> A function is called but no prototype has been supplied (<a href="#6.5.2.2">6.5.2.2</a>).
22910 <li> The arguments in a function call do not agree in number and type with those of the
22913 <li> A value is given to an object of an enumerated type other than by assignment of an
22914 enumeration constant that is a member of that type, or an enumeration object that has
22915 the same type, or the value of a function that returns the same enumerated type
22920 <li> A constant expression is used as the controlling expression of a selection statement
22922 <!--page 500 -->
22923 <li> An incorrectly formed preprocessing group is encountered while skipping a
22926 <!--page 501 -->
22927 </ul>
22931 <pre>
22932 (informative)
22933 Portability issues</pre>
22934 This annex collects some information about portability that appears in this International
22935 Standard.
22939 The following are unspecified:
22940 <ul>
22942 <li> The termination status returned to the hosted environment if the return type of main
22944 <li> The behavior of the display device if a printing character is written when the active
22946 <li> The behavior of the display device if a backspace character is written when the active
22948 <li> The behavior of the display device if a horizontal tab character is written when the
22949 active position is at or past the last defined horizontal tabulation position (<a href="#5.2.2">5.2.2</a>).
22950 <li> The behavior of the display device if a vertical tab character is written when the active
22951 position is at or past the last defined vertical tabulation position (<a href="#5.2.2">5.2.2</a>).
22952 <li> How an extended source character that does not correspond to a universal character
22953 name counts toward the significant initial characters in an external identifier (<a href="#5.2.4.1">5.2.4.1</a>).
22955 <li> The value of padding bytes when storing values in structures or unions (<a href="#6.2.6.1">6.2.6.1</a>).
22956 <li> The value of a union member other than the last one stored into (<a href="#6.2.6.1">6.2.6.1</a>).
22957 <li> The representation used when storing a value in an object that has more than one
22959 <li> The values of any padding bits in integer representations (<a href="#6.2.6.2">6.2.6.2</a>).
22960 <li> Whether certain operators can generate negative zeros and whether a negative zero
22963 <li> The order in which subexpressions are evaluated and the order in which side effects
22964 take place, except as specified for the function-call (), &&, ||, ?:, and comma
22966 <!--page 502 -->
22967 <li> The order in which the function designator, arguments, and subexpressions within the
22969 <li> The order of side effects among compound literal initialization list expressions
22971 <li> The order in which the operands of an assignment operator are evaluated (<a href="#6.5.16">6.5.16</a>).
22972 <li> The alignment of the addressable storage unit allocated to hold a bit-field (<a href="#6.7.2.1">6.7.2.1</a>).
22973 <li> Whether a call to an inline function uses the inline definition or the external definition
22975 <li> Whether or not a size expression is evaluated when it is part of the operand of a
22976 sizeof operator and changing the value of the size expression would not affect the
22978 <li> The order in which any side effects occur among the initialization list expressions in
22981 <li> When a fully expanded macro replacement list contains a function-like macro name
22982 as its last preprocessing token and the next preprocessing token from the source file is
22983 a (, and the fully expanded replacement of that macro ends with the name of the first
22984 macro and the next preprocessing token from the source file is again a (, whether that
22986 <li> The order in which # and ## operations are evaluated during macro substitution
22988 <li> Whether errno is a macro or an identifier with external linkage (<a href="#7.5">7.5</a>).
22989 <li> The state of the floating-point status flags when execution passes from a part of the
22990 program translated with FENV_ACCESS ''off'' to a part translated with
22992 <li> The order in which feraiseexcept raises floating-point exceptions, except as
22994 <li> Whether math_errhandling is a macro or an identifier with external linkage
22996 <li> The results of the frexp functions when the specified value is not a floating-point
22998 <li> The numeric result of the ilogb functions when the correct value is outside the
23000 <li> The result of rounding when the value is out of range (<a href="#7.12.9.5">7.12.9.5</a>, <a href="#7.12.9.7">7.12.9.7</a>, <a href="#F.9.6.5">F.9.6.5</a>).
23001 <!--page 503 -->
23002 <li> The value stored by the remquo functions in the object pointed to by quo when y is
23004 <li> Whether setjmp is a macro or an identifier with external linkage (<a href="#7.13">7.13</a>).
23005 <li> Whether va_copy and va_end are macros or identifiers with external linkage
23007 <li> The hexadecimal digit before the decimal point when a non-normalized floating-point
23008 number is printed with an a or A conversion specifier (<a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.24.2.1">7.24.2.1</a>).
23009 <li> The value of the file position indicator after a successful call to the ungetc function
23010 for a text stream, or the ungetwc function for any stream, until all pushed-back
23011 characters are read or discarded (<a href="#7.19.7.11">7.19.7.11</a>, <a href="#7.24.3.10">7.24.3.10</a>).
23012 <li> The details of the value stored by the fgetpos function (<a href="#7.19.9.1">7.19.9.1</a>).
23013 <li> The details of the value returned by the ftell function for a text stream (<a href="#7.19.9.4">7.19.9.4</a>).
23014 <li> Whether the strtod, strtof, strtold, wcstod, wcstof, and wcstold
23015 functions convert a minus-signed sequence to a negative number directly or by
23016 negating the value resulting from converting the corresponding unsigned sequence
23018 <li> The order and contiguity of storage allocated by successive calls to the calloc,
23020 <li> The amount of storage allocated by a successful call to the calloc, malloc, or
23022 <li> Which of two elements that compare as equal is matched by the bsearch function
23024 <li> The order of two elements that compare as equal in an array sorted by the qsort
23026 <li> The encoding of the calendar time returned by the time function (<a href="#7.23.2.4">7.23.2.4</a>).
23027 <li> The characters stored by the strftime or wcsftime function if any of the time
23028 values being converted is outside the normal range (<a href="#7.23.3.5">7.23.3.5</a>, <a href="#7.24.5.1">7.24.5.1</a>).
23029 <li> The conversion state after an encoding error occurs (<a href="#7.24.6.3.2">7.24.6.3.2</a>, <a href="#7.24.6.3.3">7.24.6.3.3</a>, <a href="#7.24.6.4.1">7.24.6.4.1</a>,
23031 <li> The resulting value when the ''invalid'' floating-point exception is raised during
23035 <!--page 504 -->
23036 <li> Whether or when library functions in <a href="#7.12"><math.h></a> raise the ''inexact'' floating-point
23038 <li> Whether or when library functions in <a href="#7.12"><math.h></a> raise an undeserved ''underflow''
23040 <li> The exponent value stored by frexp for a NaN or infinity (<a href="#F.9.3.4">F.9.3.4</a>).
23041 <li> The numeric result returned by the lrint, llrint, lround, and llround
23042 functions if the rounded value is outside the range of the return type (<a href="#F.9.6.5">F.9.6.5</a>, <a href="#F.9.6.7">F.9.6.7</a>).
23043 <li> The sign of one part of the complex result of several math functions for certain
23044 exceptional values in IEC 60559 compatible implementations (<a href="#G.6.1.1">G.6.1.1</a>, <a href="#G.6.2.2">G.6.2.2</a>,
23045 <a href="#G.6.2.3">G.6.2.3</a>, <a href="#G.6.2.4">G.6.2.4</a>, <a href="#G.6.2.5">G.6.2.5</a>, <a href="#G.6.2.6">G.6.2.6</a>, <a href="#G.6.3.1">G.6.3.1</a>, <a href="#G.6.4.2">G.6.4.2</a>).
23046 </ul>
23050 The behavior is undefined in the following circumstances:
23051 <ul>
23052 <li> A ''shall'' or ''shall not'' requirement that appears outside of a constraint is violated
23053 (clause 4).
23054 <li> A nonempty source file does not end in a new-line character which is not immediately
23055 preceded by a backslash character or ends in a partial preprocessing token or
23057 <li> Token concatenation produces a character sequence matching the syntax of a
23059 <li> A program in a hosted environment does not define a function named main using one
23061 <li> A character not in the basic source character set is encountered in a source file, except
23062 in an identifier, a character constant, a string literal, a header name, a comment, or a
23064 <li> An identifier, comment, string literal, character constant, or header name contains an
23065 invalid multibyte character or does not begin and end in the initial shift state (<a href="#5.2.1.2">5.2.1.2</a>).
23066 <li> The same identifier has both internal and external linkage in the same translation unit
23069 <li> The value of a pointer to an object whose lifetime has ended is used (<a href="#6.2.4">6.2.4</a>).
23070 <li> The value of an object with automatic storage duration is used while it is
23071 indeterminate (<a href="#6.2.4">6.2.4</a>, <a href="#6.7.8">6.7.8</a>, <a href="#6.8">6.8</a>).
23072 <li> A trap representation is read by an lvalue expression that does not have character type
23074 <!--page 505 -->
23075 <li> A trap representation is produced by a side effect that modifies any part of the object
23076 using an lvalue expression that does not have character type (<a href="#6.2.6.1">6.2.6.1</a>).
23077 <li> The arguments to certain operators are such that could produce a negative zero result,
23079 <li> Two declarations of the same object or function specify types that are not compatible
23081 <li> Conversion to or from an integer type produces a value outside the range that can be
23083 <li> Demotion of one real floating type to another produces a value outside the range that
23086 <li> A non-array lvalue with an incomplete type is used in a context that requires the value
23088 <li> An lvalue having array type is converted to a pointer to the initial element of the
23090 <li> An attempt is made to use the value of a void expression, or an implicit or explicit
23092 <li> Conversion of a pointer to an integer type produces a value outside the range that can
23094 <li> Conversion between two pointer types produces a result that is incorrectly aligned
23096 <li> A pointer is used to call a function whose type is not compatible with the pointed-to
23100 <li> A reserved keyword token is used in translation phase 7 or 8 for some purpose other
23102 <li> A universal character name in an identifier does not designate a character whose
23104 <li> The initial character of an identifier is a universal character name designating a digit
23106 <li> Two identifiers differ only in nonsignificant characters (<a href="#6.4.2.1">6.4.2.1</a>).
23108 <!--page 506 -->
23111 delimiters, or the characters ', \, //, or /* occur in the sequence between the "
23113 <li> Between two sequence points, an object is modified more than once, or is modified
23114 and the prior value is read other than to determine the value to be stored (<a href="#6.5">6.5</a>).
23115 <li> An exceptional condition occurs during the evaluation of an expression (<a href="#6.5">6.5</a>).
23116 <li> An object has its stored value accessed other than by an lvalue of an allowable type
23118 <li> An attempt is made to modify the result of a function call, a conditional operator, an
23119 assignment operator, or a comma operator, or to access it after the next sequence
23120 point (<a href="#6.5.2.2">6.5.2.2</a>, <a href="#6.5.15">6.5.15</a>, <a href="#6.5.16">6.5.16</a>, <a href="#6.5.17">6.5.17</a>).
23121 <li> For a call to a function without a function prototype in scope, the number of
23123 <li> For call to a function without a function prototype in scope where the function is
23124 defined with a function prototype, either the prototype ends with an ellipsis or the
23125 types of the arguments after promotion are not compatible with the types of the
23127 <li> For a call to a function without a function prototype in scope where the function is not
23128 defined with a function prototype, the types of the arguments after promotion are not
23129 compatible with those of the parameters after promotion (with certain exceptions)
23131 <li> A function is defined with a type that is not compatible with the type (of the
23132 expression) pointed to by the expression that denotes the called function (<a href="#6.5.2.2">6.5.2.2</a>).
23133 <li> The operand of the unary * operator has an invalid value (<a href="#6.5.3.2">6.5.3.2</a>).
23134 <li> A pointer is converted to other than an integer or pointer type (<a href="#6.5.4">6.5.4</a>).
23135 <li> The value of the second operand of the / or % operator is zero (<a href="#6.5.5">6.5.5</a>).
23136 <li> Addition or subtraction of a pointer into, or just beyond, an array object and an
23137 integer type produces a result that does not point into, or just beyond, the same array
23139 <li> Addition or subtraction of a pointer into, or just beyond, an array object and an
23140 integer type produces a result that points just beyond the array object and is used as
23142 <li> Pointers that do not point into, or just beyond, the same array object are subtracted
23144 <!--page 507 -->
23145 <li> An array subscript is out of range, even if an object is apparently accessible with the
23146 given subscript (as in the lvalue expression a[1][7] given the declaration int
23148 <li> The result of subtracting two pointers is not representable in an object of type
23150 <li> An expression is shifted by a negative number or by an amount greater than or equal
23152 <li> An expression having signed promoted type is left-shifted and either the value of the
23153 expression is negative or the result of shifting would be not be representable in the
23155 <li> Pointers that do not point to the same aggregate or union (nor just beyond the same
23157 <li> An object is assigned to an inexactly overlapping object or to an exactly overlapping
23159 <li> An expression that is required to be an integer constant expression does not have an
23160 integer type; has operands that are not integer constants, enumeration constants,
23161 character constants, sizeof expressions whose results are integer constants, or
23162 immediately-cast floating constants; or contains casts (outside operands to sizeof
23163 operators) other than conversions of arithmetic types to integer types (<a href="#6.6">6.6</a>).
23164 <li> A constant expression in an initializer is not, or does not evaluate to, one of the
23165 following: an arithmetic constant expression, a null pointer constant, an address
23166 constant, or an address constant for an object type plus or minus an integer constant
23168 <li> An arithmetic constant expression does not have arithmetic type; has operands that
23169 are not integer constants, floating constants, enumeration constants, character
23170 constants, or sizeof expressions; or contains casts (outside operands to sizeof
23171 operators) other than conversions of arithmetic types to arithmetic types (<a href="#6.6">6.6</a>).
23172 <li> The value of an object is accessed by an array-subscript [], member-access . or ->,
23173 address &, or indirection * operator or a pointer cast in creating an address constant
23175 <li> An identifier for an object is declared with no linkage and the type of the object is
23176 incomplete after its declarator, or after its init-declarator if it has an initializer (<a href="#6.7">6.7</a>).
23177 <li> A function is declared at block scope with an explicit storage-class specifier other
23179 <li> A structure or union is defined as containing no named members (<a href="#6.7.2.1">6.7.2.1</a>).
23180 <!--page 508 -->
23181 <li> An attempt is made to access, or generate a pointer to just past, a flexible array
23182 member of a structure when the referenced object provides no elements for that array
23184 <li> When the complete type is needed, an incomplete structure or union type is not
23185 completed in the same scope by another declaration of the tag that defines the content
23187 <li> An attempt is made to modify an object defined with a const-qualified type through
23189 <li> An attempt is made to refer to an object defined with a volatile-qualified type through
23191 <li> The specification of a function type includes any type qualifiers (<a href="#6.7.3">6.7.3</a>).
23192 <li> Two qualified types that are required to be compatible do not have the identically
23194 <li> An object which has been modified is accessed through a restrict-qualified pointer to
23195 a const-qualified type, or through a restrict-qualified pointer and another pointer that
23197 <li> A restrict-qualified pointer is assigned a value based on another restricted pointer
23198 whose associated block neither began execution before the block associated with this
23200 <li> A function with external linkage is declared with an inline function specifier, but is
23202 <li> Two pointer types that are required to be compatible are not identically qualified, or
23204 <li> The size expression in an array declaration is not a constant expression and evaluates
23206 <li> In a context requiring two array types to be compatible, they do not have compatible
23207 element types, or their size specifiers evaluate to unequal values (<a href="#6.7.5.2">6.7.5.2</a>).
23208 <li> A declaration of an array parameter includes the keyword static within the [ and
23209 ] and the corresponding argument does not provide access to the first element of an
23211 <li> A storage-class specifier or type qualifier modifies the keyword void as a function
23213 <li> In a context requiring two function types to be compatible, they do not have
23214 compatible return types, or their parameters disagree in use of the ellipsis terminator
23215 or the number and type of parameters (after default argument promotion, when there
23216 is no parameter type list or when one type is specified by a function definition with an
23217 <!--page 509 -->
23219 <li> The value of an unnamed member of a structure or union is used (<a href="#6.7.8">6.7.8</a>).
23220 <li> The initializer for a scalar is neither a single expression nor a single expression
23222 <li> The initializer for a structure or union object that has automatic storage duration is
23223 neither an initializer list nor a single expression that has compatible structure or union
23225 <li> The initializer for an aggregate or union, other than an array initialized by a string
23226 literal, is not a brace-enclosed list of initializers for its elements or members (<a href="#6.7.8">6.7.8</a>).
23227 <li> An identifier with external linkage is used, but in the program there does not exist
23228 exactly one external definition for the identifier, or the identifier is not used and there
23230 <li> A function definition includes an identifier list, but the types of the parameters are not
23232 <li> An adjusted parameter type in a function definition is not an object type (<a href="#6.9.1">6.9.1</a>).
23233 <li> A function that accepts a variable number of arguments is defined without a
23235 <li> The } that terminates a function is reached, and the value of the function call is used
23237 <li> An identifier for an object with internal linkage and an incomplete type is declared
23239 <li> The token defined is generated during the expansion of a #if or #elif
23240 preprocessing directive, or the use of the defined unary operator does not match
23242 <li> The #include preprocessing directive that results after expansion does not match
23244 <li> The character sequence in an #include preprocessing directive does not start with a
23246 <li> There are sequences of preprocessing tokens within the list of macro arguments that
23248 <li> The result of the preprocessing operator # is not a valid character string literal
23250 <li> The result of the preprocessing operator ## is not a valid preprocessing token
23252 <!--page 510 -->
23253 <li> The #line preprocessing directive that results after expansion does not match one of
23254 the two well-defined forms, or its digit sequence specifies zero or a number greater
23256 <li> A non-STDC #pragma preprocessing directive that is documented as causing
23257 translation failure or some other form of undefined behavior is encountered (<a href="#6.10.6">6.10.6</a>).
23258 <li> A #pragma STDC preprocessing directive does not match one of the well-defined
23260 <li> The name of a predefined macro, or the identifier defined, is the subject of a
23262 <li> An attempt is made to copy an object to an overlapping object by use of a library
23263 function, other than as explicitly allowed (e.g., memmove) (clause 7).
23264 <li> A file with the same name as one of the standard headers, not provided as part of the
23265 implementation, is placed in any of the standard places that are searched for included
23267 <li> A header is included within an external declaration or definition (<a href="#7.1.2">7.1.2</a>).
23268 <li> A function, object, type, or macro that is specified as being declared or defined by
23269 some standard header is used before any header that declares or defines it is included
23271 <li> A standard header is included while a macro is defined with the same name as a
23273 <li> The program attempts to declare a library function itself, rather than via a standard
23275 <li> The program declares or defines a reserved identifier, other than as allowed by <a href="#7.1.4">7.1.4</a>
23277 <li> The program removes the definition of a macro whose name begins with an
23279 <li> An argument to a library function has an invalid value or a type not expected by a
23281 <li> The pointer passed to a library function array parameter does not have a value such
23283 <li> The macro definition of assert is suppressed in order to access an actual function
23286 <li> The CX_LIMITED_RANGE, FENV_ACCESS, or FP_CONTRACT pragma is used in
23287 any context other than outside all external declarations or preceding all explicit
23288 <!--page 511 -->
23289 declarations and statements inside a compound statement (<a href="#7.3.4">7.3.4</a>, <a href="#7.6.1">7.6.1</a>, <a href="#7.12.2">7.12.2</a>).
23290 <li> The value of an argument to a character handling function is neither equal to the value
23292 <li> A macro definition of errno is suppressed in order to access an actual object, or the
23294 <li> Part of the program tests floating-point status flags, sets floating-point control modes,
23295 or runs under non-default mode settings, but was translated with the state for the
23297 <li> The exception-mask argument for one of the functions that provide access to the
23298 floating-point status flags has a nonzero value not obtained by bitwise OR of the
23300 <li> The fesetexceptflag function is used to set floating-point status flags that were
23301 not specified in the call to the fegetexceptflag function that provided the value
23303 <li> The argument to fesetenv or feupdateenv is neither an object set by a call to
23304 fegetenv or feholdexcept, nor is it an environment macro (<a href="#7.6.4.3">7.6.4.3</a>, <a href="#7.6.4.4">7.6.4.4</a>).
23305 <li> The value of the result of an integer arithmetic or conversion function cannot be
23306 represented (<a href="#7.8.2.1">7.8.2.1</a>, <a href="#7.8.2.2">7.8.2.2</a>, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.8.2.4">7.8.2.4</a>, <a href="#7.20.6.1">7.20.6.1</a>, <a href="#7.20.6.2">7.20.6.2</a>, <a href="#7.20.1">7.20.1</a>).
23307 <li> The program modifies the string pointed to by the value returned by the setlocale
23309 <li> The program modifies the structure pointed to by the value returned by the
23311 <li> A macro definition of math_errhandling is suppressed or the program defines
23313 <li> An argument to a floating-point classification or comparison macro is not of real
23315 <li> A macro definition of setjmp is suppressed in order to access an actual function, or
23317 <li> An invocation of the setjmp macro occurs other than in an allowed context
23319 <li> The longjmp function is invoked to restore a nonexistent environment (<a href="#7.13.2.1">7.13.2.1</a>).
23320 <li> After a longjmp, there is an attempt to access the value of an object of automatic
23321 storage class with non-volatile-qualified type, local to the function containing the
23322 invocation of the corresponding setjmp macro, that was changed between the
23324 <!--page 512 -->
23325 <li> The program specifies an invalid pointer to a signal handler function (<a href="#7.14.1.1">7.14.1.1</a>).
23326 <li> A signal handler returns when the signal corresponded to a computational exception
23328 <li> A signal occurs as the result of calling the abort or raise function, and the signal
23330 <li> A signal occurs other than as the result of calling the abort or raise function, and
23331 the signal handler refers to an object with static storage duration other than by
23332 assigning a value to an object declared as volatile sig_atomic_t, or calls any
23333 function in the standard library other than the abort function, the _Exit function,
23335 <li> The value of errno is referred to after a signal occurred other than as the result of
23336 calling the abort or raise function and the corresponding signal handler obtained
23338 <li> A signal is generated by an asynchronous signal handler (<a href="#7.14.1.1">7.14.1.1</a>).
23339 <li> A function with a variable number of arguments attempts to access its varying
23340 arguments other than through a properly declared and initialized va_list object, or
23341 before the va_start macro is invoked (<a href="#7.15">7.15</a>, <a href="#7.15.1.1">7.15.1.1</a>, <a href="#7.15.1.4">7.15.1.4</a>).
23342 <li> The macro va_arg is invoked using the parameter ap that was passed to a function
23344 <li> A macro definition of va_start, va_arg, va_copy, or va_end is suppressed in
23345 order to access an actual function, or the program defines an external identifier with
23347 <li> The va_start or va_copy macro is invoked without a corresponding invocation
23348 of the va_end macro in the same function, or vice versa (<a href="#7.15.1">7.15.1</a>, <a href="#7.15.1.2">7.15.1.2</a>, <a href="#7.15.1.3">7.15.1.3</a>,
23350 <li> The type parameter to the va_arg macro is not such that a pointer to an object of
23352 <li> The va_arg macro is invoked when there is no actual next argument, or with a
23353 specified type that is not compatible with the promoted type of the actual next
23355 <li> The va_copy or va_start macro is called to initialize a va_list that was
23356 previously initialized by either macro without an intervening invocation of the
23357 va_end macro for the same va_list (<a href="#7.15.1.2">7.15.1.2</a>, <a href="#7.15.1.4">7.15.1.4</a>).
23358 <li> The parameter parmN of a va_start macro is declared with the register
23359 storage class, with a function or array type, or with a type that is not compatible with
23360 the type that results after application of the default argument promotions (<a href="#7.15.1.4">7.15.1.4</a>).
23361 <!--page 513 -->
23362 <li> The member designator parameter of an offsetof macro is an invalid right
23363 operand of the . operator for the type parameter, or designates a bit-field (<a href="#7.17">7.17</a>).
23364 <li> The argument in an instance of one of the integer-constant macros is not a decimal,
23365 octal, or hexadecimal constant, or it has a value that exceeds the limits for the
23367 <li> A byte input/output function is applied to a wide-oriented stream, or a wide character
23369 <li> Use is made of any portion of a file beyond the most recent wide character written to
23371 <li> The value of a pointer to a FILE object is used after the associated file is closed
23373 <li> The stream for the fflush function points to an input stream or to an update stream
23375 <li> The string pointed to by the mode argument in a call to the fopen function does not
23377 <li> An output operation on an update stream is followed by an input operation without an
23378 intervening call to the fflush function or a file positioning function, or an input
23379 operation on an update stream is followed by an output operation with an intervening
23381 <li> An attempt is made to use the contents of the array that was supplied in a call to the
23383 <li> There are insufficient arguments for the format in a call to one of the formatted
23384 input/output functions, or an argument does not have an appropriate type (<a href="#7.19.6.1">7.19.6.1</a>,
23385 <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a>).
23386 <li> The format in a call to one of the formatted input/output functions or to the
23387 strftime or wcsftime function is not a valid multibyte character sequence that
23388 begins and ends in its initial shift state (<a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.23.3.5">7.23.3.5</a>, <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a>,
23390 <li> In a call to one of the formatted output functions, a precision appears with a
23391 conversion specifier other than those described (<a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.24.2.1">7.24.2.1</a>).
23392 <li> A conversion specification for a formatted output function uses an asterisk to denote
23393 an argument-supplied field width or precision, but the corresponding argument is not
23395 <li> A conversion specification for a formatted output function uses a # or 0 flag with a
23396 conversion specifier other than those described (<a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.24.2.1">7.24.2.1</a>).
23397 <!--page 514 -->
23398 <li> A conversion specification for one of the formatted input/output functions uses a
23399 length modifier with a conversion specifier other than those described (<a href="#7.19.6.1">7.19.6.1</a>,
23400 <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a>).
23401 <li> An s conversion specifier is encountered by one of the formatted output functions,
23402 and the argument is missing the null terminator (unless a precision is specified that
23403 does not require null termination) (<a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.24.2.1">7.24.2.1</a>).
23404 <li> An n conversion specification for one of the formatted input/output functions includes
23405 any flags, an assignment-suppressing character, a field width, or a precision (<a href="#7.19.6.1">7.19.6.1</a>,
23406 <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a>).
23407 <li> A % conversion specifier is encountered by one of the formatted input/output
23408 functions, but the complete conversion specification is not exactly %% (<a href="#7.19.6.1">7.19.6.1</a>,
23409 <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a>).
23410 <li> An invalid conversion specification is found in the format for one of the formatted
23411 input/output functions, or the strftime or wcsftime function (<a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.19.6.2">7.19.6.2</a>,
23412 <a href="#7.23.3.5">7.23.3.5</a>, <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a>, <a href="#7.24.5.1">7.24.5.1</a>).
23413 <li> The number of characters transmitted by a formatted output function is greater than
23414 INT_MAX (<a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.19.6.3">7.19.6.3</a>, <a href="#7.19.6.8">7.19.6.8</a>, <a href="#7.19.6.10">7.19.6.10</a>).
23415 <li> The result of a conversion by one of the formatted input functions cannot be
23416 represented in the corresponding object, or the receiving object does not have an
23418 <li> A c, s, or [ conversion specifier is encountered by one of the formatted input
23419 functions, and the array pointed to by the corresponding argument is not large enough
23420 to accept the input sequence (and a null terminator if the conversion specifier is s or
23422 <li> A c, s, or [ conversion specifier with an l qualifier is encountered by one of the
23423 formatted input functions, but the input is not a valid multibyte character sequence
23424 that begins in the initial shift state (<a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.2">7.24.2.2</a>).
23425 <li> The input item for a %p conversion by one of the formatted input functions is not a
23426 value converted earlier during the same program execution (<a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.2">7.24.2.2</a>).
23427 <li> The vfprintf, vfscanf, vprintf, vscanf, vsnprintf, vsprintf,
23428 vsscanf, vfwprintf, vfwscanf, vswprintf, vswscanf, vwprintf, or
23429 vwscanf function is called with an improperly initialized va_list argument, or
23430 the argument is used (other than in an invocation of va_end) after the function
23431 returns (<a href="#7.19.6.8">7.19.6.8</a>, <a href="#7.19.6.9">7.19.6.9</a>, <a href="#7.19.6.10">7.19.6.10</a>, <a href="#7.19.6.11">7.19.6.11</a>, <a href="#7.19.6.12">7.19.6.12</a>, <a href="#7.19.6.13">7.19.6.13</a>, <a href="#7.19.6.14">7.19.6.14</a>,
23432 <a href="#7.24.2.5">7.24.2.5</a>, <a href="#7.24.2.6">7.24.2.6</a>, <a href="#7.24.2.7">7.24.2.7</a>, <a href="#7.24.2.8">7.24.2.8</a>, <a href="#7.24.2.9">7.24.2.9</a>, <a href="#7.24.2.10">7.24.2.10</a>).
23433 <li> The contents of the array supplied in a call to the fgets, gets, or fgetws function
23434 are used after a read error occurred (<a href="#7.19.7.2">7.19.7.2</a>, <a href="#7.19.7.7">7.19.7.7</a>, <a href="#7.24.3.2">7.24.3.2</a>).
23435 <!--page 515 -->
23436 <li> The file position indicator for a binary stream is used after a call to the ungetc
23438 <li> The file position indicator for a stream is used after an error occurred during a call to
23439 the fread or fwrite function (<a href="#7.19.8.1">7.19.8.1</a>, <a href="#7.19.8.2">7.19.8.2</a>).
23440 <li> A partial element read by a call to the fread function is used (<a href="#7.19.8.1">7.19.8.1</a>).
23441 <li> The fseek function is called for a text stream with a nonzero offset and either the
23442 offset was not returned by a previous successful call to the ftell function on a
23443 stream associated with the same file or whence is not SEEK_SET (<a href="#7.19.9.2">7.19.9.2</a>).
23444 <li> The fsetpos function is called to set a position that was not returned by a previous
23445 successful call to the fgetpos function on a stream associated with the same file
23447 <li> A non-null pointer returned by a call to the calloc, malloc, or realloc function
23449 <li> The value of a pointer that refers to space deallocated by a call to the free or
23451 <li> The pointer argument to the free or realloc function does not match a pointer
23452 earlier returned by calloc, malloc, or realloc, or the space has been
23453 deallocated by a call to free or realloc (<a href="#7.20.3.2">7.20.3.2</a>, <a href="#7.20.3.4">7.20.3.4</a>).
23454 <li> The value of the object allocated by the malloc function is used (<a href="#7.20.3.3">7.20.3.3</a>).
23455 <li> The value of any bytes in a new object allocated by the realloc function beyond
23457 <li> The program executes more than one call to the exit function (<a href="#7.20.4.3">7.20.4.3</a>).
23458 <li> During the call to a function registered with the atexit function, a call is made to
23459 the longjmp function that would terminate the call to the registered function
23461 <li> The string set up by the getenv or strerror function is modified by the program
23463 <li> A command is executed through the system function in a way that is documented as
23464 causing termination or some other form of undefined behavior (<a href="#7.20.4.6">7.20.4.6</a>).
23465 <li> A searching or sorting utility function is called with an invalid pointer argument, even
23467 <li> The comparison function called by a searching or sorting utility function alters the
23468 contents of the array being searched or sorted, or returns ordering values
23470 <!--page 516 -->
23471 <li> The array being searched by the bsearch function does not have its elements in
23473 <li> The current conversion state is used by a multibyte/wide character conversion
23475 <li> A string or wide string utility function is instructed to access an array beyond the end
23477 <li> A string or wide string utility function is called with an invalid pointer argument, even
23479 <li> The contents of the destination array are used after a call to the strxfrm,
23480 strftime, wcsxfrm, or wcsftime function in which the specified length was
23481 too small to hold the entire null-terminated result (<a href="#7.21.4.5">7.21.4.5</a>, <a href="#7.23.3.5">7.23.3.5</a>, <a href="#7.24.4.4.4">7.24.4.4.4</a>,
23483 <li> The first argument in the very first call to the strtok or wcstok is a null pointer
23485 <li> The type of an argument to a type-generic macro is not compatible with the type of
23487 <li> A complex argument is supplied for a generic parameter of a type-generic macro that
23489 <li> The argument corresponding to an s specifier without an l qualifier in a call to the
23490 fwprintf function does not point to a valid multibyte character sequence that
23492 <li> In a call to the wcstok function, the object pointed to by ptr does not have the
23493 value stored by the previous call for the same wide string (<a href="#7.24.4.5.7">7.24.4.5.7</a>).
23495 <li> The value of an argument of type wint_t to a wide character classification or case
23496 mapping function is neither equal to the value of WEOF nor representable as a
23498 <li> The iswctype function is called using a different LC_CTYPE category from the
23499 one in effect for the call to the wctype function that returned the description
23501 <li> The towctrans function is called using a different LC_CTYPE category from the
23502 one in effect for the call to the wctrans function that returned the description
23504 <!--page 517 -->
23505 </ul>
23508 <p><!--para 1 -->
23509 A conforming implementation is required to document its choice of behavior in each of
23510 the areas listed in this subclause. The following are implementation-defined:
23513 <p><!--para 1 -->
23514 <ul>
23515 <li> How a diagnostic is identified (<a href="#3.10">3.10</a>, <a href="#5.1.1.3">5.1.1.3</a>).
23516 <li> Whether each nonempty sequence of white-space characters other than new-line is
23517 retained or replaced by one space character in translation phase 3 (<a href="#5.1.1.2">5.1.1.2</a>).
23518 </ul>
23521 <p><!--para 1 -->
23522 <ul>
23523 <li> The mapping between physical source file multibyte characters and the source
23525 <li> The name and type of the function called at program startup in a freestanding
23527 <li> The effect of program termination in a freestanding environment (<a href="#5.1.2.1">5.1.2.1</a>).
23528 <li> An alternative manner in which the main function may be defined (<a href="#5.1.2.2.1">5.1.2.2.1</a>).
23529 <li> The values given to the strings pointed to by the argv argument to main (<a href="#5.1.2.2.1">5.1.2.2.1</a>).
23531 <li> The set of signals, their semantics, and their default handling (<a href="#7.14">7.14</a>).
23532 <li> Signal values other than SIGFPE, SIGILL, and SIGSEGV that correspond to a
23534 <li> Signals for which the equivalent of signal(sig, SIG_IGN); is executed at
23536 <li> The set of environment names and the method for altering the environment list used
23538 <li> The manner of execution of the string by the system function (<a href="#7.20.4.6">7.20.4.6</a>).
23539 </ul>
23542 <p><!--para 1 -->
23543 <ul>
23544 <li> Which additional multibyte characters may appear in identifiers and their
23546 <li> The number of significant initial characters in an identifier (<a href="#5.2.4.1">5.2.4.1</a>, <a href="#6.4.2">6.4.2</a>).
23547 <!--page 518 -->
23548 </ul>
23551 <p><!--para 1 -->
23552 <ul>
23555 <li> The unique value of the member of the execution character set produced for each of
23557 <li> The value of a char object into which has been stored any character other than a
23559 <li> Which of signed char or unsigned char has the same range, representation,
23561 <li> The mapping of members of the source character set (in character constants and string
23562 literals) to members of the execution character set (<a href="#6.4.4.4">6.4.4.4</a>, <a href="#5.1.1.2">5.1.1.2</a>).
23563 <li> The value of an integer character constant containing more than one character or
23564 containing a character or escape sequence that does not map to a single-byte
23566 <li> The value of a wide character constant containing more than one multibyte character,
23567 or containing a multibyte character or escape sequence not represented in the
23569 <li> The current locale used to convert a wide character constant consisting of a single
23570 multibyte character that maps to a member of the extended execution character set
23572 <li> The current locale used to convert a wide string literal into corresponding wide
23574 <li> The value of a string literal containing a multibyte character or escape sequence not
23576 </ul>
23579 <p><!--para 1 -->
23580 <ul>
23581 <li> Any extended integer types that exist in the implementation (<a href="#6.2.5">6.2.5</a>).
23582 <li> Whether signed integer types are represented using sign and magnitude, two's
23583 complement, or ones' complement, and whether the extraordinary value is a trap
23585 <li> The rank of any extended integer type relative to another extended integer type with
23587 <li> The result of, or the signal raised by, converting an integer to a signed integer type
23588 when the value cannot be represented in an object of that type (<a href="#6.3.1.3">6.3.1.3</a>).
23589 <!--page 519 -->
23591 </ul>
23594 <p><!--para 1 -->
23595 <ul>
23596 <li> The accuracy of the floating-point operations and of the library functions in
23597 <a href="#7.12"><math.h></a> and <a href="#7.3"><complex.h></a> that return floating-point results (<a href="#5.2.4.2.2">5.2.4.2.2</a>).
23598 <li> The accuracy of the conversions between floating-point internal representations and
23599 string representations performed by the library functions in <a href="#7.19"><stdio.h></a>,
23600 <a href="#7.20"><stdlib.h></a>, and <a href="#7.24"><wchar.h></a> (<a href="#5.2.4.2.2">5.2.4.2.2</a>).
23601 <li> The rounding behaviors characterized by non-standard values of FLT_ROUNDS
23603 <li> The evaluation methods characterized by non-standard negative values of
23605 <li> The direction of rounding when an integer is converted to a floating-point number that
23607 <li> The direction of rounding when a floating-point number is converted to a narrower
23609 <li> How the nearest representable value or the larger or smaller representable value
23610 immediately adjacent to the nearest representable value is chosen for certain floating
23612 <li> Whether and how floating expressions are contracted when not disallowed by the
23615 <li> Additional floating-point exceptions, rounding modes, environments, and
23618 </ul>
23621 <p><!--para 1 -->
23622 <ul>
23623 <li> The result of converting a pointer to an integer or vice versa (<a href="#6.3.2.3">6.3.2.3</a>).
23624 <li> The size of the result of subtracting two pointers to elements of the same array
23626 <!--page 520 -->
23627 </ul>
23630 <p><!--para 1 -->
23631 <ul>
23632 <li> The extent to which suggestions made by using the register storage-class
23634 <li> The extent to which suggestions made by using the inline function specifier are
23636 </ul>
23638 <h4><a name="J.3.9" href="#J.3.9">J.3.9 Structures, unions, enumerations, and bit-fields</a></h4>
23639 <p><!--para 1 -->
23640 <ul>
23641 <li> Whether a ''plain'' int bit-field is treated as a signed int bit-field or as an
23643 <li> Allowable bit-field types other than _Bool, signed int, and unsigned int
23645 <li> Whether a bit-field can straddle a storage-unit boundary (<a href="#6.7.2.1">6.7.2.1</a>).
23647 <li> The alignment of non-bit-field members of structures (<a href="#6.7.2.1">6.7.2.1</a>). This should present
23648 no problem unless binary data written by one implementation is read by another.
23650 </ul>
23653 <p><!--para 1 -->
23654 <ul>
23655 <li> What constitutes an access to an object that has volatile-qualified type (<a href="#6.7.3">6.7.3</a>).
23656 </ul>
23659 <p><!--para 1 -->
23660 <ul>
23661 <li> The locations within #pragma directives where header name preprocessing tokens
23663 <li> How sequences in both forms of header names are mapped to headers or external
23665 <li> Whether the value of a character constant in a constant expression that controls
23666 conditional inclusion matches the value of the same character constant in the
23668 <li> Whether the value of a single-character character constant in a constant expression
23670 <li> The places that are searched for an included < > delimited header, and how the places
23674 <li> The method by which preprocessing tokens (possibly resulting from macro
23675 expansion) in a #include directive are combined into a header name (<a href="#6.10.2">6.10.2</a>).
23676 <!--page 521 -->
23678 <li> Whether the # operator inserts a \ character before the \ character that begins a
23679 universal character name in a character constant or string literal (<a href="#6.10.3.2">6.10.3.2</a>).
23680 <li> The behavior on each recognized non-STDC #pragma directive (<a href="#6.10.6">6.10.6</a>).
23681 <li> The definitions for __DATE__ and __TIME__ when respectively, the date and
23683 </ul>
23686 <p><!--para 1 -->
23687 <ul>
23688 <li> Any library facilities available to a freestanding program, other than the minimal set
23690 <li> The format of the diagnostic printed by the assert macro (<a href="#7.2.1.1">7.2.1.1</a>).
23691 <li> The representation of the floating-point status flags stored by the
23693 <li> Whether the feraiseexcept function raises the ''inexact'' floating-point
23694 exception in addition to the ''overflow'' or ''underflow'' floating-point exception
23698 <li> The types defined for float_t and double_t when the value of the
23700 <li> Domain errors for the mathematics functions, other than those required by this
23702 <li> The values returned by the mathematics functions on domain errors (<a href="#7.12.1">7.12.1</a>).
23703 <li> The values returned by the mathematics functions on underflow range errors, whether
23704 errno is set to the value of the macro ERANGE when the integer expression
23705 math_errhandling & MATH_ERRNO is nonzero, and whether the ''underflow''
23706 floating-point exception is raised when the integer expression math_errhandling
23708 <li> Whether a domain error occurs or zero is returned when an fmod function has a
23710 <li> Whether a domain error occurs or zero is returned when a remainder function has
23712 <li> The base-2 logarithm of the modulus used by the remquo functions in reducing the
23714 <!--page 522 -->
23715 <li> Whether a domain error occurs or zero is returned when a remquo function has a
23717 <li> Whether the equivalent of signal(sig, SIG_DFL); is executed prior to the call
23718 of a signal handler, and, if not, the blocking of signals that is performed (<a href="#7.14.1.1">7.14.1.1</a>).
23720 <li> Whether the last line of a text stream requires a terminating new-line character
23722 <li> Whether space characters that are written out to a text stream immediately before a
23724 <li> The number of null characters that may be appended to data written to a binary
23726 <li> Whether the file position indicator of an append-mode stream is initially positioned at
23728 <li> Whether a write on a text stream causes the associated file to be truncated beyond that
23733 <li> Whether the same file can be simultaneously open multiple times (<a href="#7.19.3">7.19.3</a>).
23734 <li> The nature and choice of encodings used for multibyte characters in files (<a href="#7.19.3">7.19.3</a>).
23736 <li> The effect if a file with the new name exists prior to a call to the rename function
23738 <li> Whether an open temporary file is removed upon abnormal program termination
23740 <li> Which changes of mode are permitted (if any), and under what circumstances
23742 <li> The style used to print an infinity or NaN, and the meaning of any n-char or n-wchar
23743 sequence printed for a NaN (<a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.24.2.1">7.24.2.1</a>).
23744 <li> The output for %p conversion in the fprintf or fwprintf function (<a href="#7.19.6.1">7.19.6.1</a>,
23746 <li> The interpretation of a - character that is neither the first nor the last character, nor
23747 the second where a ^ character is the first, in the scanlist for %[ conversion in the
23748 fscanf or fwscanf function (<a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.1">7.24.2.1</a>).
23749 <!--page 523 -->
23750 <li> The set of sequences matched by a %p conversion and the interpretation of the
23751 corresponding input item in the fscanf or fwscanf function (<a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.2">7.24.2.2</a>).
23752 <li> The value to which the macro errno is set by the fgetpos, fsetpos, or ftell
23753 functions on failure (<a href="#7.19.9.1">7.19.9.1</a>, <a href="#7.19.9.3">7.19.9.3</a>, <a href="#7.19.9.4">7.19.9.4</a>).
23754 <li> The meaning of any n-char or n-wchar sequence in a string representing a NaN that is
23755 converted by the strtod, strtof, strtold, wcstod, wcstof, or wcstold
23757 <li> Whether or not the strtod, strtof, strtold, wcstod, wcstof, or wcstold
23758 function sets errno to ERANGE when underflow occurs (<a href="#7.20.1.3">7.20.1.3</a>, <a href="#7.24.4.1.1">7.24.4.1.1</a>).
23759 <li> Whether the calloc, malloc, and realloc functions return a null pointer or a
23760 pointer to an allocated object when the size requested is zero (<a href="#7.20.3">7.20.3</a>).
23761 <li> Whether open streams with unwritten buffered data are flushed, open streams are
23762 closed, or temporary files are removed when the abort or _Exit function is called
23764 <li> The termination status returned to the host environment by the abort, exit, or
23765 _Exit function (<a href="#7.20.4.1">7.20.4.1</a>, <a href="#7.20.4.3">7.20.4.3</a>, <a href="#7.20.4.4">7.20.4.4</a>).
23766 <li> The value returned by the system function when its argument is not a null pointer
23769 <li> The range and precision of times representable in clock_t and time_t (<a href="#7.23">7.23</a>).
23771 <li> The replacement string for the %Z specifier to the strftime, and wcsftime
23772 functions in the "C" locale (<a href="#7.23.3.5">7.23.3.5</a>, <a href="#7.24.5.1">7.24.5.1</a>).
23773 <li> Whether the functions in <a href="#7.12"><math.h></a> honor the rounding direction mode in an
23774 IEC 60559 conformant implementation, unless explicitly specified otherwise (<a href="#F.9">F.9</a>).
23775 </ul>
23778 <p><!--para 1 -->
23779 <ul>
23780 <li> The values or expressions assigned to the macros specified in the headers
23781 <a href="#7.7"><float.h></a>, <a href="#7.10"><limits.h></a>, and <a href="#7.18"><stdint.h></a> (<a href="#5.2.4.2">5.2.4.2</a>, <a href="#7.18.2">7.18.2</a>, <a href="#7.18.3">7.18.3</a>).
23782 <li> The number, order, and encoding of bytes in any object (when not explicitly specified
23785 <!--page 524 -->
23786 </ul>
23789 <p><!--para 1 -->
23790 The following characteristics of a hosted environment are locale-specific and are required
23791 to be documented by the implementation:
23792 <ul>
23793 <li> Additional members of the source and execution character sets beyond the basic
23795 <li> The presence, meaning, and representation of additional multibyte characters in the
23797 <li> The shift states used for the encoding of multibyte characters (<a href="#5.2.1.2">5.2.1.2</a>).
23802 <li> The sets of characters tested for by the isalpha, isblank, islower, ispunct,
23803 isspace, isupper, iswalpha, iswblank, iswlower, iswpunct,
23804 iswspace, or iswupper functions (<a href="#7.4.1.2">7.4.1.2</a>, <a href="#7.4.1.3">7.4.1.3</a>, <a href="#7.4.1.7">7.4.1.7</a>, <a href="#7.4.1.9">7.4.1.9</a>, <a href="#7.4.1.10">7.4.1.10</a>,
23805 <a href="#7.4.1.11">7.4.1.11</a>, <a href="#7.25.2.1.2">7.25.2.1.2</a>, <a href="#7.25.2.1.3">7.25.2.1.3</a>, <a href="#7.25.2.1.7">7.25.2.1.7</a>, <a href="#7.25.2.1.9">7.25.2.1.9</a>, <a href="#7.25.2.1.10">7.25.2.1.10</a>, <a href="#7.25.2.1.11">7.25.2.1.11</a>).
23807 <li> Additional subject sequences accepted by the numeric conversion functions (<a href="#7.20.1">7.20.1</a>,
23809 <li> The collation sequence of the execution character set (<a href="#7.21.4.3">7.21.4.3</a>, <a href="#7.24.4.4.2">7.24.4.4.2</a>).
23810 <li> The contents of the error message strings set up by the strerror function
23812 <li> The formats for time and date (<a href="#7.23.3.5">7.23.3.5</a>, <a href="#7.24.5.1">7.24.5.1</a>).
23813 <li> Character mappings that are supported by the towctrans function (<a href="#7.25.1">7.25.1</a>).
23814 <li> Character classifications that are supported by the iswctype function (<a href="#7.25.1">7.25.1</a>).
23815 <!--page 525 -->
23816 </ul>
23819 <p><!--para 1 -->
23820 The following extensions are widely used in many systems, but are not portable to all
23821 implementations. The inclusion of any extension that may cause a strictly conforming
23822 program to become invalid renders an implementation nonconforming. Examples of such
23823 extensions are new keywords, extra library functions declared in standard headers, or
23824 predefined macros with names that do not begin with an underscore.
23827 <p><!--para 1 -->
23828 In a hosted environment, the main function receives a third argument, char *envp[],
23829 that points to a null-terminated array of pointers to char, each of which points to a string
23830 that provides information about the environment for this execution of the program
23834 <p><!--para 1 -->
23835 Characters other than the underscore _, letters, and digits, that are not part of the basic
23836 source character set (such as the dollar sign $, or characters in national character sets)
23840 <p><!--para 1 -->
23841 All characters in identifiers (with or without external linkage) are significant (<a href="#6.4.2">6.4.2</a>).
23844 <p><!--para 1 -->
23845 A function identifier, or the identifier of an object the declaration of which contains the
23849 <p><!--para 1 -->
23850 String literals are modifiable (in which case, identical string literals should denote distinct
23854 <p><!--para 1 -->
23855 Additional arithmetic types, such as __int128 or double double, and their
23856 appropriate conversions are defined (<a href="#6.2.5">6.2.5</a>, <a href="#6.3.1">6.3.1</a>). Additional floating types may have
23857 more range or precision than long double, may be used for evaluating expressions of
23858 other floating types, and may be used to define float_t or double_t.
23859 <!--page 526 -->
23862 <p><!--para 1 -->
23863 A pointer to an object or to void may be cast to a pointer to a function, allowing data to
23865 <p><!--para 2 -->
23866 A pointer to a function may be cast to a pointer to an object or to void, allowing a
23867 function to be inspected or modified (for example, by a debugger) (<a href="#6.5.4">6.5.4</a>).
23870 <p><!--para 1 -->
23871 A bit-field may be declared with a type other than _Bool, unsigned int, or
23875 <p><!--para 1 -->
23876 The fortran function specifier may be used in a function declaration to indicate that
23877 calls suitable for FORTRAN should be generated, or that a different representation for the
23881 <p><!--para 1 -->
23882 The asm keyword may be used to insert assembly language directly into the translator
23883 output (<a href="#6.8">6.8</a>). The most common implementation is via a statement of the form:
23884 <pre>
23885 asm ( character-string-literal );</pre>
23888 <p><!--para 1 -->
23889 There may be more than one external definition for the identifier of an object, with or
23890 without the explicit use of the keyword extern; if the definitions disagree, or more than
23894 <p><!--para 1 -->
23895 Macro names that do not begin with an underscore, describing the translation and
23896 execution environments, are defined by the implementation before translation begins
23900 <p><!--para 1 -->
23901 If any floating-point status flags are set on normal termination after all calls to functions
23902 registered by the atexit function have been made (see <a href="#7.20.4.3">7.20.4.3</a>), the implementation
23903 writes some diagnostics indicating the fact to the stderr stream, if it is still open,
23904 <!--page 527 -->
23907 <p><!--para 1 -->
23908 Handlers for specific signals are called with extra arguments in addition to the signal
23911 <h4><a name="J.5.15" href="#J.5.15">J.5.15 Additional stream types and file-opening modes</a></h4>
23912 <p><!--para 1 -->
23914 <p><!--para 2 -->
23915 Additional file-opening modes may be specified by characters appended to the mode
23919 <p><!--para 1 -->
23920 The file position indicator is decremented by each successful call to the ungetc or
23921 ungetwc function for a text stream, except if its value was zero before a call (<a href="#7.19.7.11">7.19.7.11</a>,
23925 <p><!--para 1 -->
23926 Functions declared in <a href="#7.3"><complex.h></a> and <a href="#7.12"><math.h></a> raise SIGFPE to report errors
23927 instead of, or in addition to, setting errno or raising floating-point exceptions (<a href="#7.3">7.3</a>,
23929 <!--page 528 -->
23932 <ol>
23933 <li> ''The C Reference Manual'' by Dennis M. Ritchie, a version of which was
23934 published in The C Programming Language by Brian W. Kernighan and Dennis
23935 M. Ritchie, Prentice-Hall, Inc., (1978). Copyright owned by AT&T.
23936 <li> 1984 /usr/group Standard by the /usr/group Standards Committee, Santa Clara,
23937 California, USA, November 1984.
23938 <li> ANSI X3/TR-1-82 (1982), American National Dictionary for Information
23939 Processing Systems, Information Processing Systems Technical Report.
23940 <li> ANSI/IEEE 754-1985, American National Standard for Binary Floating-Point
23941 Arithmetic.
23942 <li> ANSI/IEEE 854-1988, American National Standard for Radix-Independent
23943 Floating-Point Arithmetic.
23944 <li> IEC 60559:1989, Binary floating-point arithmetic for microprocessor systems,
23945 second edition (previously designated IEC 559:1989).
23946 <li> ISO 31-11:1992, Quantities and units -- Part 11: Mathematical signs and
23947 symbols for use in the physical sciences and technology.
23948 <li> ISO/IEC 646:1991, Information technology -- ISO 7-bit coded character set for
23949 information interchange.
23950 <li> ISO/IEC 2382-1:1993, Information technology -- Vocabulary -- Part 1:
23951 Fundamental terms.
23952 <li> ISO 4217:1995, Codes for the representation of currencies and funds.
23953 <li> ISO 8601:1988, Data elements and interchange formats -- Information
23954 interchange -- Representation of dates and times.
23955 <li> ISO/IEC 9899:1990, Programming languages -- C.
23956 <li> ISO/IEC 9899/COR1:1994, Technical Corrigendum 1.
23957 <li> ISO/IEC 9899/COR2:1996, Technical Corrigendum 2.
23958 <li> ISO/IEC 9899/AMD1:1995, Amendment 1 to ISO/IEC 9899:1990 C Integrity.
23959 <li> ISO/IEC 9945-2:1993, Information technology -- Portable Operating System
23960 Interface (POSIX) -- Part 2: Shell and Utilities.
23961 <li> ISO/IEC TR 10176:1998, Information technology -- Guidelines for the
23962 preparation of programming language standards.
23963 <li> ISO/IEC 10646-1:1993, Information technology -- Universal Multiple-Octet
23964 Coded Character Set (UCS) -- Part 1: Architecture and Basic Multilingual Plane.
23965 <!--page 529 -->
23966 <li> ISO/IEC 10646-1/COR1:1996, Technical Corrigendum 1 to
23967 ISO/IEC 10646-1:1993.
23968 <li> ISO/IEC 10646-1/COR2:1998, Technical Corrigendum 2 to
23969 ISO/IEC 10646-1:1993.
23970 <li> ISO/IEC 10646-1/AMD1:1996, Amendment 1 to ISO/IEC 10646-1:1993
23971 Transformation Format for 16 planes of group 00 (UTF-16).
23972 <li> ISO/IEC 10646-1/AMD2:1996, Amendment 2 to ISO/IEC 10646-1:1993 UCS
23973 Transformation Format 8 (UTF-8).
23974 <li> ISO/IEC 10646-1/AMD3:1996, Amendment 3 to ISO/IEC 10646-1:1993.
23975 <li> ISO/IEC 10646-1/AMD4:1996, Amendment 4 to ISO/IEC 10646-1:1993.
23976 <li> ISO/IEC 10646-1/AMD5:1998, Amendment 5 to ISO/IEC 10646-1:1993 Hangul
23977 syllables.
23978 <li> ISO/IEC 10646-1/AMD6:1997, Amendment 6 to ISO/IEC 10646-1:1993 Tibetan.
23979 <li> ISO/IEC 10646-1/AMD7:1997, Amendment 7 to ISO/IEC 10646-1:1993 33
23980 additional characters.
23981 <li> ISO/IEC 10646-1/AMD8:1997, Amendment 8 to ISO/IEC 10646-1:1993.
23982 <li> ISO/IEC 10646-1/AMD9:1997, Amendment 9 to ISO/IEC 10646-1:1993
23983 Identifiers for characters.
23984 <li> ISO/IEC 10646-1/AMD10:1998, Amendment 10 to ISO/IEC 10646-1:1993
23985 Ethiopic.
23986 <li> ISO/IEC 10646-1/AMD11:1998, Amendment 11 to ISO/IEC 10646-1:1993
23987 Unified Canadian Aboriginal Syllabics.
23988 <li> ISO/IEC 10646-1/AMD12:1998, Amendment 12 to ISO/IEC 10646-1:1993
23989 Cherokee.
23990 <li> ISO/IEC 10967-1:1994, Information technology -- Language independent
23991 arithmetic -- Part 1: Integer and floating point arithmetic.
23992 <!--page 530 -->
23993 <!--page 531 -->
23994 </ol>
23997 <pre>
23998 ??? x ???, <a href="#3.18">3.18</a> , (comma punctuator), <a href="#6.5.2">6.5.2</a>, <a href="#6.7">6.7</a>, <a href="#6.7.2.1">6.7.2.1</a>, <a href="#6.7.2.2">6.7.2.2</a>,
24000 ??? x ???, <a href="#3.19">3.19</a> - (subtraction operator), <a href="#6.5.6">6.5.6</a>, <a href="#F.3">F.3</a>, <a href="#G.5.2">G.5.2</a>
24001 ! (logical negation operator), <a href="#6.5.3.3">6.5.3.3</a> - (unary minus operator), <a href="#6.5.3.3">6.5.3.3</a>, <a href="#F.3">F.3</a>
24002 != (inequality operator), <a href="#6.5.9">6.5.9</a> -- (postfix decrement operator), <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.2.4">6.5.2.4</a>
24003 # operator, <a href="#6.10.3.2">6.10.3.2</a> -- (prefix decrement operator), <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.3.1">6.5.3.1</a>
24004 # preprocessing directive, <a href="#6.10.7">6.10.7</a> -= (subtraction assignment operator), <a href="#6.5.16.2">6.5.16.2</a>
24005 # punctuator, <a href="#6.10">6.10</a> -> (structure/union pointer operator), <a href="#6.5.2.3">6.5.2.3</a>
24006 ## operator, <a href="#6.10.3.3">6.10.3.3</a> . (structure/union member operator), <a href="#6.3.2.1">6.3.2.1</a>,
24008 #elif preprocessing directive, <a href="#6.10.1">6.10.1</a> . punctuator, <a href="#6.7.8">6.7.8</a>
24009 #else preprocessing directive, <a href="#6.10.1">6.10.1</a> ... (ellipsis punctuator), <a href="#6.5.2.2">6.5.2.2</a>, <a href="#6.7.5.3">6.7.5.3</a>, <a href="#6.10.3">6.10.3</a>
24010 #endif preprocessing directive, <a href="#6.10.1">6.10.1</a> / (division operator), <a href="#6.5.5">6.5.5</a>, <a href="#F.3">F.3</a>, <a href="#G.5.1">G.5.1</a>
24011 #error preprocessing directive, <a href="#4">4</a>, <a href="#6.10.5">6.10.5</a> /* */ (comment delimiters), <a href="#6.4.9">6.4.9</a>
24012 #if preprocessing directive, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, // (comment delimiter), <a href="#6.4.9">6.4.9</a>
24013 <a href="#6.10.1">6.10.1</a>, <a href="#7.1.4">7.1.4</a> /= (division assignment operator), <a href="#6.5.16.2">6.5.16.2</a>
24014 #ifdef preprocessing directive, <a href="#6.10.1">6.10.1</a> : (colon punctuator), <a href="#6.7.2.1">6.7.2.1</a>
24015 #ifndef preprocessing directive, <a href="#6.10.1">6.10.1</a> :> (alternative spelling of ]), <a href="#6.4.6">6.4.6</a>
24016 #include preprocessing directive, <a href="#5.1.1.2">5.1.1.2</a>, ; (semicolon punctuator), <a href="#6.7">6.7</a>, <a href="#6.7.2.1">6.7.2.1</a>, <a href="#6.8.3">6.8.3</a>,
24018 #line preprocessing directive, <a href="#6.10.4">6.10.4</a> < (less-than operator), <a href="#6.5.8">6.5.8</a>
24019 #pragma preprocessing directive, <a href="#6.10.6">6.10.6</a> <% (alternative spelling of {), <a href="#6.4.6">6.4.6</a>
24020 #undef preprocessing directive, <a href="#6.10.3.5">6.10.3.5</a>, <a href="#7.1.3">7.1.3</a>, <: (alternative spelling of [), <a href="#6.4.6">6.4.6</a>
24022 % (remainder operator), <a href="#6.5.5">6.5.5</a> <<= (left-shift assignment operator), <a href="#6.5.16.2">6.5.16.2</a>
24023 %: (alternative spelling of #), <a href="#6.4.6">6.4.6</a> <= (less-than-or-equal-to operator), <a href="#6.5.8">6.5.8</a>
24024 %:%: (alternative spelling of ##), <a href="#6.4.6">6.4.6</a> <a href="#7.2"><assert.h></a> header, <a href="#7.2">7.2</a>, <a href="#B.1">B.1</a>
24025 %= (remainder assignment operator), <a href="#6.5.16.2">6.5.16.2</a> <a href="#7.3"><complex.h></a> header, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.3">7.3</a>, <a href="#7.22">7.22</a>,
24026 %> (alternative spelling of }), <a href="#6.4.6">6.4.6</a> <a href="#7.26.1">7.26.1</a>, <a href="#G.6">G.6</a>, <a href="#J.5.17">J.5.17</a>
24027 & (address operator), <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.3.2">6.5.3.2</a> <a href="#7.4"><ctype.h></a> header, <a href="#7.4">7.4</a>, <a href="#7.26.2">7.26.2</a>
24028 & (bitwise AND operator), <a href="#6.5.10">6.5.10</a> <a href="#7.5"><errno.h></a> header, <a href="#7.5">7.5</a>, <a href="#7.26.3">7.26.3</a>
24029 && (logical AND operator), <a href="#6.5.13">6.5.13</a> <a href="#7.6"><fenv.h></a> header, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.6">7.6</a>, <a href="#7.12">7.12</a>, <a href="#F">F</a>,
24031 ' ' (space character), <a href="#5.1.1.2">5.1.1.2</a>, <a href="#5.2.1">5.2.1</a>, <a href="#6.4">6.4</a>, <a href="#7.4.1.3">7.4.1.3</a>, <a href="#7.7"><float.h></a> header, <a href="#4">4</a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.7">7.7</a>, <a href="#7.20.1.3">7.20.1.3</a>,
24032 <a href="#7.4.1.10">7.4.1.10</a>, <a href="#7.25.2.1.3">7.25.2.1.3</a> <a href="#7.24.4.1.1">7.24.4.1.1</a>
24033 ( ) (cast operator), <a href="#6.5.4">6.5.4</a> <a href="#7.8"><inttypes.h></a> header, <a href="#7.8">7.8</a>, <a href="#7.26.4">7.26.4</a>
24034 ( ) (function-call operator), <a href="#6.5.2.2">6.5.2.2</a> <a href="#7.9"><iso646.h></a> header, <a href="#4">4</a>, <a href="#7.9">7.9</a>
24035 ( ) (parentheses punctuator), <a href="#6.7.5.3">6.7.5.3</a>, <a href="#6.8.4">6.8.4</a>, <a href="#6.8.5">6.8.5</a> <a href="#7.10"><limits.h></a> header, <a href="#4">4</a>, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#6.2.5">6.2.5</a>, <a href="#7.10">7.10</a>
24036 ( ){ } (compound-literal operator), <a href="#6.5.2.5">6.5.2.5</a> <a href="#7.11"><locale.h></a> header, <a href="#7.11">7.11</a>, <a href="#7.26.5">7.26.5</a>
24037 * (asterisk punctuator), <a href="#6.7.5.1">6.7.5.1</a>, <a href="#6.7.5.2">6.7.5.2</a> <a href="#7.12"><math.h></a> header, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.5">6.5</a>, <a href="#7.12">7.12</a>, <a href="#7.22">7.22</a>, <a href="#F">F</a>,
24038 * (indirection operator), <a href="#6.5.2.1">6.5.2.1</a>, <a href="#6.5.3.2">6.5.3.2</a> <a href="#F.9">F.9</a>, <a href="#J.5.17">J.5.17</a>
24039 * (multiplication operator), <a href="#6.5.5">6.5.5</a>, <a href="#F.3">F.3</a>, <a href="#G.5.1">G.5.1</a> <a href="#7.13"><setjmp.h></a> header, <a href="#7.13">7.13</a>
24040 *= (multiplication assignment operator), <a href="#6.5.16.2">6.5.16.2</a> <a href="#7.14"><signal.h></a> header, <a href="#7.14">7.14</a>, <a href="#7.26.6">7.26.6</a>
24041 + (addition operator), <a href="#6.5.2.1">6.5.2.1</a>, <a href="#6.5.3.2">6.5.3.2</a>, <a href="#6.5.6">6.5.6</a>, <a href="#F.3">F.3</a>, <a href="#7.15"><stdarg.h></a> header, <a href="#4">4</a>, <a href="#6.7.5.3">6.7.5.3</a>, <a href="#7.15">7.15</a>
24042 <a href="#G.5.2">G.5.2</a> <a href="#7.16"><stdbool.h></a> header, <a href="#4">4</a>, <a href="#7.16">7.16</a>, <a href="#7.26.7">7.26.7</a>, <a href="#H">H</a>
24043 + (unary plus operator), <a href="#6.5.3.3">6.5.3.3</a> <a href="#7.17"><stddef.h></a> header, <a href="#4">4</a>, <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.3.2.3">6.3.2.3</a>, <a href="#6.4.4.4">6.4.4.4</a>,
24044 ++ (postfix increment operator), <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.2.4">6.5.2.4</a> <a href="#6.4.5">6.4.5</a>, <a href="#6.5.3.4">6.5.3.4</a>, <a href="#6.5.6">6.5.6</a>, <a href="#7.17">7.17</a>
24045 ++ (prefix increment operator), <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.3.1">6.5.3.1</a> <a href="#7.18"><stdint.h></a> header, <a href="#4">4</a>, <a href="#5.2.4.2">5.2.4.2</a>, <a href="#6.10.1">6.10.1</a>, <a href="#7.8">7.8</a>,
24046 += (addition assignment operator), <a href="#6.5.16.2">6.5.16.2</a> <a href="#7.18">7.18</a>, <a href="#7.26.8">7.26.8</a>
24048 <!--page 532 -->
24049 <a href="#7.19"><stdio.h></a> header, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.19">7.19</a>, <a href="#7.26.9">7.26.9</a>, <a href="#F">F</a> __cplusplus macro, <a href="#6.10.8">6.10.8</a>
24050 <a href="#7.20"><stdlib.h></a> header, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.20">7.20</a>, <a href="#7.26.10">7.26.10</a>, <a href="#F">F</a> __DATE__ macro, <a href="#6.10.8">6.10.8</a>
24051 <a href="#7.21"><string.h></a> header, <a href="#7.21">7.21</a>, <a href="#7.26.11">7.26.11</a> __FILE__ macro, <a href="#6.10.8">6.10.8</a>, <a href="#7.2.1.1">7.2.1.1</a>
24052 <a href="#7.22"><tgmath.h></a> header, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</a> __func__ identifier, <a href="#6.4.2.2">6.4.2.2</a>, <a href="#7.2.1.1">7.2.1.1</a>
24053 <a href="#7.23"><time.h></a> header, <a href="#7.23">7.23</a> __LINE__ macro, <a href="#6.10.8">6.10.8</a>, <a href="#7.2.1.1">7.2.1.1</a>
24054 <a href="#7.24"><wchar.h></a> header, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.19.1">7.19.1</a>, <a href="#7.24">7.24</a>, __STDC_, <a href="#6.11.9">6.11.9</a>
24055 <a href="#7.26.12">7.26.12</a>, <a href="#F">F</a> __STDC__ macro, <a href="#6.10.8">6.10.8</a>
24056 <a href="#7.25"><wctype.h></a> header, <a href="#7.25">7.25</a>, <a href="#7.26.13">7.26.13</a> __STDC_CONSTANT_MACROS macro, <a href="#7.18.4">7.18.4</a>
24057 = (equal-sign punctuator), <a href="#6.7">6.7</a>, <a href="#6.7.2.2">6.7.2.2</a>, <a href="#6.7.8">6.7.8</a> __STDC_FORMAT_MACROS macro, <a href="#7.8.1">7.8.1</a>
24058 = (simple assignment operator), <a href="#6.5.16.1">6.5.16.1</a> __STDC_HOSTED__ macro, <a href="#6.10.8">6.10.8</a>
24059 == (equality operator), <a href="#6.5.9">6.5.9</a> __STDC_IEC_559__ macro, <a href="#6.10.8">6.10.8</a>, <a href="#F.1">F.1</a>
24061 >= (greater-than-or-equal-to operator), <a href="#6.5.8">6.5.8</a> <a href="#6.10.8">6.10.8</a>, <a href="#G.1">G.1</a>
24062 >> (right-shift operator), <a href="#6.5.7">6.5.7</a> __STDC_ISO_10646__ macro, <a href="#6.10.8">6.10.8</a>
24063 >>= (right-shift assignment operator), <a href="#6.5.16.2">6.5.16.2</a> __STDC_LIMIT_MACROS macro, <a href="#7.18.2">7.18.2</a>,
24066 [ ] (array subscript operator), <a href="#6.5.2.1">6.5.2.1</a>, <a href="#6.5.3.2">6.5.3.2</a> <a href="#6.10.8">6.10.8</a>, <a href="#7.17">7.17</a>
24067 [ ] (brackets punctuator), <a href="#6.7.5.2">6.7.5.2</a>, <a href="#6.7.8">6.7.8</a> __STDC_VERSION__ macro, <a href="#6.10.8">6.10.8</a>
24068 \ (backslash character), <a href="#5.1.1.2">5.1.1.2</a>, <a href="#5.2.1">5.2.1</a>, <a href="#6.4.4.4">6.4.4.4</a> __TIME__ macro, <a href="#6.10.8">6.10.8</a>
24069 \ (escape character), <a href="#6.4.4.4">6.4.4.4</a> __VA_ARGS__ identifier, <a href="#6.10.3">6.10.3</a>, <a href="#6.10.3.1">6.10.3.1</a>
24070 \" (double-quote escape sequence), <a href="#6.4.4.4">6.4.4.4</a>, _Bool type, <a href="#6.2.5">6.2.5</a>, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.3.1.2">6.3.1.2</a>, <a href="#6.7.2">6.7.2</a>
24071 <a href="#6.4.5">6.4.5</a>, <a href="#6.10.9">6.10.9</a> _Bool type conversions, <a href="#6.3.1.2">6.3.1.2</a>
24072 \\ (backslash escape sequence), <a href="#6.4.4.4">6.4.4.4</a>, <a href="#6.10.9">6.10.9</a> _Complex types, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.2">6.7.2</a>, <a href="#7.3.1">7.3.1</a>, <a href="#G">G</a>
24073 \' (single-quote escape sequence), <a href="#6.4.4.4">6.4.4.4</a>, <a href="#6.4.5">6.4.5</a> _Complex_I macro, <a href="#7.3.1">7.3.1</a>
24074 \0 (null character), <a href="#5.2.1">5.2.1</a>, <a href="#6.4.4.4">6.4.4.4</a>, <a href="#6.4.5">6.4.5</a> _Exit function, <a href="#7.20.4.4">7.20.4.4</a>
24075 padding of binary stream, <a href="#7.19.2">7.19.2</a> _Imaginary keyword, <a href="#G.2">G.2</a>
24076 \? (question-mark escape sequence), <a href="#6.4.4.4">6.4.4.4</a> _Imaginary types, <a href="#7.3.1">7.3.1</a>, <a href="#G">G</a>
24077 \a (alert escape sequence), <a href="#5.2.2">5.2.2</a>, <a href="#6.4.4.4">6.4.4.4</a> _Imaginary_I macro, <a href="#7.3.1">7.3.1</a>, <a href="#G.6">G.6</a>
24078 \b (backspace escape sequence), <a href="#5.2.2">5.2.2</a>, <a href="#6.4.4.4">6.4.4.4</a> _IOFBF macro, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.5.5">7.19.5.5</a>, <a href="#7.19.5.6">7.19.5.6</a>
24079 \f (form-feed escape sequence), <a href="#5.2.2">5.2.2</a>, <a href="#6.4.4.4">6.4.4.4</a>, _IOLBF macro, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.5.6">7.19.5.6</a>
24080 <a href="#7.4.1.10">7.4.1.10</a> _IONBF macro, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.5.5">7.19.5.5</a>, <a href="#7.19.5.6">7.19.5.6</a>
24081 \n (new-line escape sequence), <a href="#5.2.2">5.2.2</a>, <a href="#6.4.4.4">6.4.4.4</a>, _Pragma operator, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#6.10.9">6.10.9</a>
24082 <a href="#7.4.1.10">7.4.1.10</a> { } (braces punctuator), <a href="#6.7.2.2">6.7.2.2</a>, <a href="#6.7.2.3">6.7.2.3</a>, <a href="#6.7.8">6.7.8</a>,
24084 <a href="#6.4.4.4">6.4.4.4</a> { } (compound-literal operator), <a href="#6.5.2.5">6.5.2.5</a>
24085 \r (carriage-return escape sequence), <a href="#5.2.2">5.2.2</a>, | (bitwise inclusive OR operator), <a href="#6.5.12">6.5.12</a>
24086 <a href="#6.4.4.4">6.4.4.4</a>, <a href="#7.4.1.10">7.4.1.10</a> |= (bitwise inclusive OR assignment operator),
24087 \t (horizontal-tab escape sequence), <a href="#5.2.2">5.2.2</a>, <a href="#6.5.16.2">6.5.16.2</a>
24088 <a href="#6.4.4.4">6.4.4.4</a>, <a href="#7.4.1.3">7.4.1.3</a>, <a href="#7.4.1.10">7.4.1.10</a>, <a href="#7.25.2.1.3">7.25.2.1.3</a> || (logical OR operator), <a href="#6.5.14">6.5.14</a>
24089 \U (universal character names), <a href="#6.4.3">6.4.3</a> ~ (bitwise complement operator), <a href="#6.5.3.3">6.5.3.3</a>
24091 \v (vertical-tab escape sequence), <a href="#5.2.2">5.2.2</a>, <a href="#6.4.4.4">6.4.4.4</a>, abort function, <a href="#7.2.1.1">7.2.1.1</a>, <a href="#7.14.1.1">7.14.1.1</a>, <a href="#7.19.3">7.19.3</a>,
24095 ^ (bitwise exclusive OR operator), <a href="#6.5.11">6.5.11</a> complex, <a href="#7.3.8">7.3.8</a>, <a href="#G.6.4">G.6.4</a>
24096 ^= (bitwise exclusive OR assignment operator), integer, <a href="#7.8.2.1">7.8.2.1</a>, <a href="#7.20.6.1">7.20.6.1</a>
24097 <a href="#6.5.16.2">6.5.16.2</a> real, <a href="#7.12.7">7.12.7</a>, <a href="#F.9.4">F.9.4</a>
24100 <!--page 533 -->
24103 acos functions, <a href="#7.12.4.1">7.12.4.1</a>, <a href="#F.9.1.1">F.9.1.1</a> declarator, <a href="#6.7.5.2">6.7.5.2</a>
24105 acosh functions, <a href="#7.12.5.1">7.12.5.1</a>, <a href="#F.9.2.1">F.9.2.1</a> multidimensional, <a href="#6.5.2.1">6.5.2.1</a>
24108 actual argument, <a href="#3.3">3.3</a> subscript operator ([ ]), <a href="#6.5.2.1">6.5.2.1</a>, <a href="#6.5.3.2">6.5.3.2</a>
24109 actual parameter (deprecated), <a href="#3.3">3.3</a> subscripting, <a href="#6.5.2.1">6.5.2.1</a>
24110 addition assignment operator (+=), <a href="#6.5.16.2">6.5.16.2</a> type, <a href="#6.2.5">6.2.5</a>
24111 addition operator (+), <a href="#6.5.2.1">6.5.2.1</a>, <a href="#6.5.3.2">6.5.3.2</a>, <a href="#6.5.6">6.5.6</a>, <a href="#F.3">F.3</a>, type conversion, <a href="#6.3.2.1">6.3.2.1</a>
24112 <a href="#G.5.2">G.5.2</a> variable length, <a href="#6.7.5">6.7.5</a>, <a href="#6.7.5.2">6.7.5.2</a>
24113 additive expressions, <a href="#6.5.6">6.5.6</a>, <a href="#G.5.2">G.5.2</a> arrow operator (->), <a href="#6.5.2.3">6.5.2.3</a>
24115 address operator (&), <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.3.2">6.5.3.2</a> ASCII code set, <a href="#5.2.1.1">5.2.1.1</a>
24116 aggregate initialization, <a href="#6.7.8">6.7.8</a> asctime function, <a href="#7.23.3.1">7.23.3.1</a>
24117 aggregate types, <a href="#6.2.5">6.2.5</a> asin functions, <a href="#7.12.4.2">7.12.4.2</a>, <a href="#F.9.1.2">F.9.1.2</a>
24118 alert escape sequence (\a), <a href="#5.2.2">5.2.2</a>, <a href="#6.4.4.4">6.4.4.4</a> asin type-generic macro, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</a>
24119 aliasing, <a href="#6.5">6.5</a> asinh functions, <a href="#7.12.5.2">7.12.5.2</a>, <a href="#F.9.2.2">F.9.2.2</a>
24120 alignment, <a href="#3.2">3.2</a> asinh type-generic macro, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</a>
24121 pointer, <a href="#6.2.5">6.2.5</a>, <a href="#6.3.2.3">6.3.2.3</a> asm keyword, <a href="#J.5.10">J.5.10</a>
24122 structure/union member, <a href="#6.7.2.1">6.7.2.1</a> assert macro, <a href="#7.2.1.1">7.2.1.1</a>
24123 allocated storage, order and contiguity, <a href="#7.20.3">7.20.3</a> assert.h header, <a href="#7.2">7.2</a>, <a href="#B.1">B.1</a>
24127 bitwise assignment (&=), <a href="#6.5.16.2">6.5.16.2</a> expression, <a href="#6.5.16">6.5.16</a>
24128 logical (&&), <a href="#6.5.13">6.5.13</a> operators, <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.16">6.5.16</a>
24131 ANSI/IEEE 854, <a href="#F.1">F.1</a> asterisk punctuator (*), <a href="#6.7.5.1">6.7.5.1</a>, <a href="#6.7.5.2">6.7.5.2</a>
24132 argc (main function parameter), <a href="#5.1.2.2.1">5.1.2.2.1</a> atan functions, <a href="#7.12.4.3">7.12.4.3</a>, <a href="#F.9.1.3">F.9.1.3</a>
24133 argument, <a href="#3.3">3.3</a> atan type-generic macro, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</a>
24134 array, <a href="#6.9.1">6.9.1</a> atan2 functions, <a href="#7.12.4.4">7.12.4.4</a>, <a href="#F.9.1.4">F.9.1.4</a>
24135 default promotions, <a href="#6.5.2.2">6.5.2.2</a> atan2 type-generic macro, <a href="#7.22">7.22</a>
24136 function, <a href="#6.5.2.2">6.5.2.2</a>, <a href="#6.9.1">6.9.1</a> atanh functions, <a href="#7.12.5.3">7.12.5.3</a>, <a href="#F.9.2.3">F.9.2.3</a>
24137 macro, substitution, <a href="#6.10.3.1">6.10.3.1</a> atanh type-generic macro, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</a>
24138 argument, complex, <a href="#7.3.9.1">7.3.9.1</a> atexit function, <a href="#7.20.4.2">7.20.4.2</a>, <a href="#7.20.4.3">7.20.4.3</a>, <a href="#7.20.4.4">7.20.4.4</a>,
24139 argv (main function parameter), <a href="#5.1.2.2.1">5.1.2.2.1</a> <a href="#J.5.13">J.5.13</a>
24140 arithmetic constant expression, <a href="#6.6">6.6</a> atof function, <a href="#7.20.1">7.20.1</a>, <a href="#7.20.1.1">7.20.1.1</a>
24141 arithmetic conversions, usual, see usual arithmetic atoi function, <a href="#7.20.1">7.20.1</a>, <a href="#7.20.1.2">7.20.1.2</a>
24143 arithmetic operators atoll function, <a href="#7.20.1">7.20.1</a>, <a href="#7.20.1.2">7.20.1.2</a>
24144 additive, <a href="#6.5.6">6.5.6</a>, <a href="#G.5.2">G.5.2</a> auto storage-class specifier, <a href="#6.7.1">6.7.1</a>, <a href="#6.9">6.9</a>
24145 bitwise, <a href="#6.5.10">6.5.10</a>, <a href="#6.5.11">6.5.11</a>, <a href="#6.5.12">6.5.12</a> automatic storage duration, <a href="#5.2.3">5.2.3</a>, <a href="#6.2.4">6.2.4</a>
24147 multiplicative, <a href="#6.5.5">6.5.5</a>, <a href="#G.5.1">G.5.1</a> backslash character (\), <a href="#5.1.1.2">5.1.1.2</a>, <a href="#5.2.1">5.2.1</a>, <a href="#6.4.4.4">6.4.4.4</a>
24148 shift, <a href="#6.5.7">6.5.7</a> backslash escape sequence (\\), <a href="#6.4.4.4">6.4.4.4</a>, <a href="#6.10.9">6.10.9</a>
24149 unary, <a href="#6.5.3.3">6.5.3.3</a> backspace escape sequence (\b), <a href="#5.2.2">5.2.2</a>, <a href="#6.4.4.4">6.4.4.4</a>
24150 arithmetic types, <a href="#6.2.5">6.2.5</a> basic character set, <a href="#3.6">3.6</a>, <a href="#3.7.2">3.7.2</a>, <a href="#5.2.1">5.2.1</a>
24152 <!--page 534 -->
24154 binary streams, <a href="#7.19.2">7.19.2</a>, <a href="#7.19.7.11">7.19.7.11</a>, <a href="#7.19.9.2">7.19.9.2</a>, calloc function, <a href="#7.20.3">7.20.3</a>, <a href="#7.20.3.1">7.20.3.1</a>, <a href="#7.20.3.2">7.20.3.2</a>,
24156 bit, <a href="#3.5">3.5</a> carg functions, <a href="#7.3.9.1">7.3.9.1</a>, <a href="#G.6">G.6</a>
24157 high order, <a href="#3.6">3.6</a> carg type-generic macro, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</a>
24158 low order, <a href="#3.6">3.6</a> carriage-return escape sequence (\r), <a href="#5.2.2">5.2.2</a>,
24159 bit-field, <a href="#6.7.2.1">6.7.2.1</a> <a href="#6.4.4.4">6.4.4.4</a>, <a href="#7.4.1.10">7.4.1.10</a>
24160 bitand macro, <a href="#7.9">7.9</a> case label, <a href="#6.8.1">6.8.1</a>, <a href="#6.8.4.2">6.8.4.2</a>
24164 AND assignment (&=), <a href="#6.5.16.2">6.5.16.2</a> extensible, <a href="#7.25.3.2">7.25.3.2</a>
24165 complement (~), <a href="#6.5.3.3">6.5.3.3</a> casin functions, <a href="#7.3.5.2">7.3.5.2</a>, <a href="#G.6">G.6</a>
24167 exclusive OR assignment (^=), <a href="#6.5.16.2">6.5.16.2</a> casinh functions, <a href="#7.3.6.2">7.3.6.2</a>, <a href="#G.6.2.2">G.6.2.2</a>
24169 inclusive OR assignment (|=), <a href="#6.5.16.2">6.5.16.2</a> cast expression, <a href="#6.5.4">6.5.4</a>
24171 blank character, <a href="#7.4.1.3">7.4.1.3</a> catan functions, <a href="#7.3.5.3">7.3.5.3</a>, <a href="#G.6">G.6</a>
24172 block, <a href="#6.8">6.8</a>, <a href="#6.8.2">6.8.2</a>, <a href="#6.8.4">6.8.4</a>, <a href="#6.8.5">6.8.5</a> type-generic macro for, <a href="#7.22">7.22</a>
24173 block scope, <a href="#6.2.1">6.2.1</a> catanh functions, <a href="#7.3.6.3">7.3.6.3</a>, <a href="#G.6.2.3">G.6.2.3</a>
24175 bold type convention, <a href="#6.1">6.1</a> cbrt functions, <a href="#7.12.7.1">7.12.7.1</a>, <a href="#F.9.4.1">F.9.4.1</a>
24177 boolean type, <a href="#6.3.1.2">6.3.1.2</a> ccos functions, <a href="#7.3.5.4">7.3.5.4</a>, <a href="#G.6">G.6</a>
24178 boolean type conversion, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.3.1.2">6.3.1.2</a> type-generic macro for, <a href="#7.22">7.22</a>
24179 braces punctuator ({ }), <a href="#6.7.2.2">6.7.2.2</a>, <a href="#6.7.2.3">6.7.2.3</a>, <a href="#6.7.8">6.7.8</a>, ccosh functions, <a href="#7.3.6.4">7.3.6.4</a>, <a href="#G.6.2.4">G.6.2.4</a>
24181 brackets operator ([ ]), <a href="#6.5.2.1">6.5.2.1</a>, <a href="#6.5.3.2">6.5.3.2</a> ceil functions, <a href="#7.12.9.1">7.12.9.1</a>, <a href="#F.9.6.1">F.9.6.1</a>
24182 brackets punctuator ([ ]), <a href="#6.7.5.2">6.7.5.2</a>, <a href="#6.7.8">6.7.8</a> ceil type-generic macro, <a href="#7.22">7.22</a>
24185 broken-down time, <a href="#7.23.1">7.23.1</a>, <a href="#7.23.2.3">7.23.2.3</a>, <a href="#7.23.3">7.23.3</a>, cexp functions, <a href="#7.3.7.1">7.3.7.1</a>, <a href="#G.6.3.1">G.6.3.1</a>
24186 <a href="#7.23.3.1">7.23.3.1</a>, <a href="#7.23.3.3">7.23.3.3</a>, <a href="#7.23.3.4">7.23.3.4</a>, <a href="#7.23.3.5">7.23.3.5</a> type-generic macro for, <a href="#7.22">7.22</a>
24187 bsearch function, <a href="#7.20.5">7.20.5</a>, <a href="#7.20.5.1">7.20.5.1</a> cexp2 function, <a href="#7.26.1">7.26.1</a>
24188 btowc function, <a href="#7.24.6.1.1">7.24.6.1.1</a> cexpm1 function, <a href="#7.26.1">7.26.1</a>
24189 BUFSIZ macro, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.2">7.19.2</a>, <a href="#7.19.5.5">7.19.5.5</a> char type, <a href="#6.2.5">6.2.5</a>, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.7.2">6.7.2</a>
24190 byte, <a href="#3.6">3.6</a>, <a href="#6.5.3.4">6.5.3.4</a> char type conversion, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.3.1.3">6.3.1.3</a>, <a href="#6.3.1.4">6.3.1.4</a>,
24192 byte-oriented stream, <a href="#7.19.2">7.19.2</a> CHAR_BIT macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>
24194 <a href="#C">C</a> program, <a href="#5.1.1.1">5.1.1.1</a> CHAR_MIN macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>
24195 <a href="#C">C</a>++, <a href="#7.8.1">7.8.1</a>, <a href="#7.18.2">7.18.2</a>, <a href="#7.18.3">7.18.3</a>, <a href="#7.18.4">7.18.4</a> character, <a href="#3.7">3.7</a>, <a href="#3.7.1">3.7.1</a>
24196 cabs functions, <a href="#7.3.8.1">7.3.8.1</a>, <a href="#G.6">G.6</a> character array initialization, <a href="#6.7.8">6.7.8</a>
24197 type-generic macro for, <a href="#7.22">7.22</a> character case mapping functions, <a href="#7.4.2">7.4.2</a>
24198 cacos functions, <a href="#7.3.5.1">7.3.5.1</a>, <a href="#G.6.1.1">G.6.1.1</a> wide character, <a href="#7.25.3.1">7.25.3.1</a>
24200 cacosh functions, <a href="#7.3.6.1">7.3.6.1</a>, <a href="#G.6.2.1">G.6.2.1</a> character classification functions, <a href="#7.4.1">7.4.1</a>
24201 type-generic macro for, <a href="#7.22">7.22</a> wide character, <a href="#7.25.2.1">7.25.2.1</a>
24202 calendar time, <a href="#7.23.1">7.23.1</a>, <a href="#7.23.2.2">7.23.2.2</a>, <a href="#7.23.2.3">7.23.2.3</a>, <a href="#7.23.2.4">7.23.2.4</a>, extensible, <a href="#7.25.2.2">7.25.2.2</a>
24203 <a href="#7.23.3.2">7.23.3.2</a>, <a href="#7.23.3.3">7.23.3.3</a>, <a href="#7.23.3.4">7.23.3.4</a> character constant, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#5.2.1">5.2.1</a>, <a href="#6.4.4.4">6.4.4.4</a>
24204 <!--page 535 -->
24205 character display semantics, <a href="#5.2.2">5.2.2</a> complex.h header, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.3">7.3</a>, <a href="#7.22">7.22</a>, <a href="#7.26.1">7.26.1</a>,
24206 character handling header, <a href="#7.4">7.4</a>, <a href="#7.11.1.1">7.11.1.1</a> <a href="#G.6">G.6</a>, <a href="#J.5.17">J.5.17</a>
24210 character string literal, see string literal compound assignment, <a href="#6.5.16.2">6.5.16.2</a>
24211 character type conversion, <a href="#6.3.1.1">6.3.1.1</a> compound literals, <a href="#6.5.2.5">6.5.2.5</a>
24212 character types, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.8">6.7.8</a> compound statement, <a href="#6.8.2">6.8.2</a>
24213 cimag functions, <a href="#7.3.9.2">7.3.9.2</a>, <a href="#7.3.9.4">7.3.9.4</a>, <a href="#G.6">G.6</a> compound-literal operator (( ){ }), <a href="#6.5.2.5">6.5.2.5</a>
24214 cimag type-generic macro, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</a> concatenation functions
24220 extensible, <a href="#7.25.2.2">7.25.2.2</a> conditional inclusion, <a href="#6.10.1">6.10.1</a>
24221 clearerr function, <a href="#7.19.10.1">7.19.10.1</a> conditional operator (? :), <a href="#6.5.15">6.5.15</a>
24223 clock function, <a href="#7.23.2.1">7.23.2.1</a> conj functions, <a href="#7.3.9.3">7.3.9.3</a>, <a href="#G.6">G.6</a>
24224 clock_t type, <a href="#7.23.1">7.23.1</a>, <a href="#7.23.2.1">7.23.2.1</a> conj type-generic macro, <a href="#7.22">7.22</a>
24225 CLOCKS_PER_SEC macro, <a href="#7.23.1">7.23.1</a>, <a href="#7.23.2.1">7.23.2.1</a> const type qualifier, <a href="#6.7.3">6.7.3</a>
24226 clog functions, <a href="#7.3.7.2">7.3.7.2</a>, <a href="#G.6.3.2">G.6.3.2</a> const-qualified type, <a href="#6.2.5">6.2.5</a>, <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.7.3">6.7.3</a>
24227 type-generic macro for, <a href="#7.22">7.22</a> constant expression, <a href="#6.6">6.6</a>, <a href="#F.7.4">F.7.4</a>
24229 clog1p function, <a href="#7.26.1">7.26.1</a> as primary expression, <a href="#6.5.1">6.5.1</a>
24231 collating sequences, <a href="#5.2.1">5.2.1</a> enumeration, <a href="#6.2.1">6.2.1</a>, <a href="#6.4.4.3">6.4.4.3</a>
24234 comma punctuator (,), <a href="#6.5.2">6.5.2</a>, <a href="#6.7">6.7</a>, <a href="#6.7.2.1">6.7.2.1</a>, <a href="#6.7.2.2">6.7.2.2</a>, integer, <a href="#6.4.4.1">6.4.4.1</a>
24235 <a href="#6.7.2.3">6.7.2.3</a>, <a href="#6.7.8">6.7.8</a> octal, <a href="#6.4.4.1">6.4.4.1</a>
24236 command processor, <a href="#7.20.4.6">7.20.4.6</a> constraint, <a href="#3.8">3.8</a>, <a href="#4">4</a>
24237 comment delimiters (/* */ and //), <a href="#6.4.9">6.4.9</a> content of structure/union/enumeration, <a href="#6.7.2.3">6.7.2.3</a>
24238 comments, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#6.4">6.4</a>, <a href="#6.4.9">6.4.9</a> contiguity of allocated storage, <a href="#7.20.3">7.20.3</a>
24240 common initial sequence, <a href="#6.5.2.3">6.5.2.3</a> contracted expression, <a href="#6.5">6.5</a>, <a href="#7.12.2">7.12.2</a>, <a href="#F.6">F.6</a>
24241 common real type, <a href="#6.3.1.8">6.3.1.8</a> control character, <a href="#5.2.1">5.2.1</a>, <a href="#7.4">7.4</a>
24243 comparison functions, <a href="#7.20.5">7.20.5</a>, <a href="#7.20.5.1">7.20.5.1</a>, <a href="#7.20.5.2">7.20.5.2</a> conversion, <a href="#6.3">6.3</a>
24248 compatible type, <a href="#6.2.7">6.2.7</a>, <a href="#6.7.2">6.7.2</a>, <a href="#6.7.3">6.7.3</a>, <a href="#6.7.5">6.7.5</a> boolean, <a href="#6.3.1.2">6.3.1.2</a>
24249 compl macro, <a href="#7.9">7.9</a> boolean, characters, and integers, <a href="#6.3.1.1">6.3.1.1</a>
24250 complement operator (~), <a href="#6.5.3.3">6.5.3.3</a> by assignment, <a href="#6.5.16.1">6.5.16.1</a>
24252 complex numbers, <a href="#6.2.5">6.2.5</a>, <a href="#G">G</a> complex types, <a href="#6.3.1.6">6.3.1.6</a>
24253 complex type conversion, <a href="#6.3.1.6">6.3.1.6</a>, <a href="#6.3.1.7">6.3.1.7</a> explicit, <a href="#6.3">6.3</a>
24255 complex types, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.2">6.7.2</a>, <a href="#G">G</a> function argument, <a href="#6.5.2.2">6.5.2.2</a>, <a href="#6.9.1">6.9.1</a>
24256 <!--page 536 -->
24257 function designators, <a href="#6.3.2.1">6.3.2.1</a> type-generic macro for, <a href="#7.22">7.22</a>
24258 function parameter, <a href="#6.9.1">6.9.1</a> csinh functions, <a href="#7.3.6.5">7.3.6.5</a>, <a href="#G.6.2.5">G.6.2.5</a>
24260 imaginary and complex, <a href="#G.4.3">G.4.3</a> csqrt functions, <a href="#7.3.8.3">7.3.8.3</a>, <a href="#G.6.4.2">G.6.4.2</a>
24262 lvalues, <a href="#6.3.2.1">6.3.2.1</a> ctan functions, <a href="#7.3.5.6">7.3.5.6</a>, <a href="#G.6">G.6</a>
24263 pointer, <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.3.2.3">6.3.2.3</a> type-generic macro for, <a href="#7.22">7.22</a>
24264 real and complex, <a href="#6.3.1.7">6.3.1.7</a> ctanh functions, <a href="#7.3.6.6">7.3.6.6</a>, <a href="#G.6.2.6">G.6.2.6</a>
24265 real and imaginary, <a href="#G.4.2">G.4.2</a> type-generic macro for, <a href="#7.22">7.22</a>
24266 real floating and integer, <a href="#6.3.1.4">6.3.1.4</a>, <a href="#F.3">F.3</a>, <a href="#F.4">F.4</a> ctgamma function, <a href="#7.26.1">7.26.1</a>
24267 real floating types, <a href="#6.3.1.5">6.3.1.5</a>, <a href="#F.3">F.3</a> ctime function, <a href="#7.23.3.2">7.23.3.2</a>
24268 signed and unsigned integers, <a href="#6.3.1.3">6.3.1.3</a> ctype.h header, <a href="#7.4">7.4</a>, <a href="#7.26.2">7.26.2</a>
24272 conversion functions data stream, see streams
24273 multibyte/wide character, <a href="#7.20.7">7.20.7</a> date and time header, <a href="#7.23">7.23</a>
24275 restartable, <a href="#7.24.6.3">7.24.6.3</a> DBL_DIG macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
24276 multibyte/wide string, <a href="#7.20.8">7.20.8</a> DBL_EPSILON macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
24277 restartable, <a href="#7.24.6.4">7.24.6.4</a> DBL_MANT_DIG macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
24278 numeric, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.20.1">7.20.1</a> DBL_MAX macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
24279 wide string, <a href="#7.8.2.4">7.8.2.4</a>, <a href="#7.24.4.1">7.24.4.1</a> DBL_MAX_10_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
24280 single byte/wide character, <a href="#7.24.6.1">7.24.6.1</a> DBL_MAX_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
24282 wide character, <a href="#7.24.5">7.24.5</a> DBL_MIN_10_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
24283 conversion specifier, <a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.1">7.24.2.1</a>, DBL_MIN_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
24285 conversion state, <a href="#7.20.7">7.20.7</a>, <a href="#7.24.6">7.24.6</a>, <a href="#7.24.6.2.1">7.24.6.2.1</a>, decimal digit, <a href="#5.2.1">5.2.1</a>
24286 <a href="#7.24.6.3">7.24.6.3</a>, <a href="#7.24.6.3.2">7.24.6.3.2</a>, <a href="#7.24.6.3.3">7.24.6.3.3</a>, <a href="#7.24.6.4">7.24.6.4</a>, decimal-point character, <a href="#7.1.1">7.1.1</a>, <a href="#7.11.2.1">7.11.2.1</a>
24287 <a href="#7.24.6.4.1">7.24.6.4.1</a>, <a href="#7.24.6.4.2">7.24.6.4.2</a> DECIMAL_DIG macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.19.6.1">7.19.6.1</a>,
24288 conversion state functions, <a href="#7.24.6.2">7.24.6.2</a> <a href="#7.20.1.3">7.20.1.3</a>, <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.4.1.1">7.24.4.1.1</a>, <a href="#F.5">F.5</a>
24292 copysign functions, <a href="#7.3.9.4">7.3.9.4</a>, <a href="#7.12.11.1">7.12.11.1</a>, <a href="#F.3">F.3</a>, pointer, <a href="#6.7.5.1">6.7.5.1</a>
24297 cos functions, <a href="#7.12.4.5">7.12.4.5</a>, <a href="#F.9.1.5">F.9.1.5</a> declarator type derivation, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.5">6.7.5</a>
24298 cos type-generic macro, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</a> decrement operators, see arithmetic operators,
24299 cosh functions, <a href="#7.12.5.4">7.12.5.4</a>, <a href="#F.9.2.4">F.9.2.4</a> increment and decrement
24300 cosh type-generic macro, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</a> default argument promotions, <a href="#6.5.2.2">6.5.2.2</a>
24301 cpow functions, <a href="#7.3.8.2">7.3.8.2</a>, <a href="#G.6.4.1">G.6.4.1</a> default initialization, <a href="#6.7.8">6.7.8</a>
24302 type-generic macro for, <a href="#7.22">7.22</a> default label, <a href="#6.8.1">6.8.1</a>, <a href="#6.8.4.2">6.8.4.2</a>
24303 cproj functions, <a href="#7.3.9.4">7.3.9.4</a>, <a href="#G.6">G.6</a> define preprocessing directive, <a href="#6.10.3">6.10.3</a>
24304 cproj type-generic macro, <a href="#7.22">7.22</a> defined operator, <a href="#6.10.1">6.10.1</a>, <a href="#6.10.8">6.10.8</a>
24305 creal functions, <a href="#7.3.9.5">7.3.9.5</a>, <a href="#G.6">G.6</a> definition, <a href="#6.7">6.7</a>
24306 creal type-generic macro, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</a> function, <a href="#6.9.1">6.9.1</a>
24307 csin functions, <a href="#7.3.5.5">7.3.5.5</a>, <a href="#G.6">G.6</a> derived declarator types, <a href="#6.2.5">6.2.5</a>
24308 <!--page 537 -->
24309 derived types, <a href="#6.2.5">6.2.5</a> end-of-file indicator, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.5.3">7.19.5.3</a>, <a href="#7.19.7.1">7.19.7.1</a>,
24310 designated initializer, <a href="#6.7.8">6.7.8</a> <a href="#7.19.7.5">7.19.7.5</a>, <a href="#7.19.7.6">7.19.7.6</a>, <a href="#7.19.7.11">7.19.7.11</a>, <a href="#7.19.9.2">7.19.9.2</a>,
24311 destringizing, <a href="#6.10.9">6.10.9</a> <a href="#7.19.9.3">7.19.9.3</a>, <a href="#7.19.10.1">7.19.10.1</a>, <a href="#7.19.10.2">7.19.10.2</a>, <a href="#7.24.3.1">7.24.3.1</a>,
24313 diagnostic message, <a href="#3.10">3.10</a>, <a href="#5.1.1.3">5.1.1.3</a> end-of-file macro, see EOF macro
24315 diagnostics header, <a href="#7.2">7.2</a> endif preprocessing directive, <a href="#6.10.1">6.10.1</a>
24316 difftime function, <a href="#7.23.2.2">7.23.2.2</a> enum type, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.2">6.7.2</a>, <a href="#6.7.2.2">6.7.2.2</a>
24317 digit, <a href="#5.2.1">5.2.1</a>, <a href="#7.4">7.4</a> enumerated type, <a href="#6.2.5">6.2.5</a>
24318 digraphs, <a href="#6.4.6">6.4.6</a> enumeration, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.2.2">6.7.2.2</a>
24319 direct input/output functions, <a href="#7.19.8">7.19.8</a> enumeration constant, <a href="#6.2.1">6.2.1</a>, <a href="#6.4.4.3">6.4.4.3</a>
24320 display device, <a href="#5.2.2">5.2.2</a> enumeration content, <a href="#6.7.2.3">6.7.2.3</a>
24321 div function, <a href="#7.20.6.2">7.20.6.2</a> enumeration members, <a href="#6.7.2.2">6.7.2.2</a>
24323 division assignment operator (/=), <a href="#6.5.16.2">6.5.16.2</a> enumeration tag, <a href="#6.2.3">6.2.3</a>, <a href="#6.7.2.3">6.7.2.3</a>
24324 division operator (/), <a href="#6.5.5">6.5.5</a>, <a href="#F.3">F.3</a>, <a href="#G.5.1">G.5.1</a> enumerator, <a href="#6.7.2.2">6.7.2.2</a>
24326 documentation of implementation, <a href="#4">4</a> environment functions, <a href="#7.20.4">7.20.4</a>
24327 domain error, <a href="#7.12.1">7.12.1</a>, <a href="#7.12.4.1">7.12.4.1</a>, <a href="#7.12.4.2">7.12.4.2</a>, <a href="#7.12.4.4">7.12.4.4</a>, environment list, <a href="#7.20.4.5">7.20.4.5</a>
24328 <a href="#7.12.5.1">7.12.5.1</a>, <a href="#7.12.5.3">7.12.5.3</a>, <a href="#7.12.6.5">7.12.6.5</a>, <a href="#7.12.6.7">7.12.6.7</a>, environmental considerations, <a href="#5.2">5.2</a>
24329 <a href="#7.12.6.8">7.12.6.8</a>, <a href="#7.12.6.9">7.12.6.9</a>, <a href="#7.12.6.10">7.12.6.10</a>, <a href="#7.12.6.11">7.12.6.11</a>, environmental limits, <a href="#5.2.4">5.2.4</a>, <a href="#7.13.1.1">7.13.1.1</a>, <a href="#7.19.2">7.19.2</a>,
24330 <a href="#7.12.7.4">7.12.7.4</a>, <a href="#7.12.7.5">7.12.7.5</a>, <a href="#7.12.8.4">7.12.8.4</a>, <a href="#7.12.9.5">7.12.9.5</a>, <a href="#7.19.3">7.19.3</a>, <a href="#7.19.4.4">7.19.4.4</a>, <a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.20.2.1">7.20.2.1</a>, <a href="#7.20.4.2">7.20.4.2</a>,
24331 <a href="#7.12.9.7">7.12.9.7</a>, <a href="#7.12.10.1">7.12.10.1</a>, <a href="#7.12.10.2">7.12.10.2</a>, <a href="#7.12.10.3">7.12.10.3</a> <a href="#7.24.2.1">7.24.2.1</a>
24332 dot operator (.), <a href="#6.5.2.3">6.5.2.3</a> EOF macro, <a href="#7.4">7.4</a>, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.5.1">7.19.5.1</a>, <a href="#7.19.5.2">7.19.5.2</a>,
24333 double _Complex type, <a href="#6.2.5">6.2.5</a> <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.19.6.7">7.19.6.7</a>, <a href="#7.19.6.9">7.19.6.9</a>, <a href="#7.19.6.11">7.19.6.11</a>,
24334 double _Complex type conversion, <a href="#6.3.1.6">6.3.1.6</a>, <a href="#7.19.6.14">7.19.6.14</a>, <a href="#7.19.7.1">7.19.7.1</a>, <a href="#7.19.7.3">7.19.7.3</a>, <a href="#7.19.7.4">7.19.7.4</a>,
24335 <a href="#6.3.1.7">6.3.1.7</a>, <a href="#6.3.1.8">6.3.1.8</a> <a href="#7.19.7.5">7.19.7.5</a>, <a href="#7.19.7.6">7.19.7.6</a>, <a href="#7.19.7.9">7.19.7.9</a>, <a href="#7.19.7.10">7.19.7.10</a>,
24336 double _Imaginary type, <a href="#G.2">G.2</a> <a href="#7.19.7.11">7.19.7.11</a>, <a href="#7.24.1">7.24.1</a>, <a href="#7.24.2.2">7.24.2.2</a>, <a href="#7.24.2.4">7.24.2.4</a>,
24337 double type, <a href="#6.2.5">6.2.5</a>, <a href="#6.4.4.2">6.4.4.2</a>, <a href="#6.7.2">6.7.2</a>, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.6">7.24.2.6</a>, <a href="#7.24.2.8">7.24.2.8</a>, <a href="#7.24.2.10">7.24.2.10</a>, <a href="#7.24.2.12">7.24.2.12</a>,
24338 <a href="#7.24.2.2">7.24.2.2</a>, <a href="#F.2">F.2</a> <a href="#7.24.3.4">7.24.3.4</a>, <a href="#7.24.6.1.1">7.24.6.1.1</a>, <a href="#7.24.6.1.2">7.24.6.1.2</a>
24339 double type conversion, <a href="#6.3.1.4">6.3.1.4</a>, <a href="#6.3.1.5">6.3.1.5</a>, <a href="#6.3.1.7">6.3.1.7</a>, equal-sign punctuator (=), <a href="#6.7">6.7</a>, <a href="#6.7.2.2">6.7.2.2</a>, <a href="#6.7.8">6.7.8</a>
24341 double-precision arithmetic, <a href="#5.1.2.3">5.1.2.3</a> equality expressions, <a href="#6.5.9">6.5.9</a>
24342 double-quote escape sequence (\"), <a href="#6.4.4.4">6.4.4.4</a>, equality operator (==), <a href="#6.5.9">6.5.9</a>
24343 <a href="#6.4.5">6.4.5</a>, <a href="#6.10.9">6.10.9</a> ERANGE macro, <a href="#7.5">7.5</a>, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.8.2.4">7.8.2.4</a>, <a href="#7.12.1">7.12.1</a>,
24344 double_t type, <a href="#7.12">7.12</a>, <a href="#J.5.6">J.5.6</a> <a href="#7.20.1.3">7.20.1.3</a>, <a href="#7.20.1.4">7.20.1.4</a>, <a href="#7.24.4.1.1">7.24.4.1.1</a>, <a href="#7.24.4.1.2">7.24.4.1.2</a>, see
24345 also range error
24346 EDOM macro, <a href="#7.5">7.5</a>, <a href="#7.12.1">7.12.1</a>, see also domain error erf functions, <a href="#7.12.8.1">7.12.8.1</a>, <a href="#F.9.5.1">F.9.5.1</a>
24348 EILSEQ macro, <a href="#7.5">7.5</a>, <a href="#7.19.3">7.19.3</a>, <a href="#7.24.3.1">7.24.3.1</a>, <a href="#7.24.3.3">7.24.3.3</a>, erfc functions, <a href="#7.12.8.2">7.12.8.2</a>, <a href="#F.9.5.2">F.9.5.2</a>
24349 <a href="#7.24.6.3.2">7.24.6.3.2</a>, <a href="#7.24.6.3.3">7.24.6.3.3</a>, <a href="#7.24.6.4.1">7.24.6.4.1</a>, <a href="#7.24.6.4.2">7.24.6.4.2</a>, erfc type-generic macro, <a href="#7.22">7.22</a>
24350 see also encoding error errno macro, <a href="#7.1.3">7.1.3</a>, <a href="#7.3.2">7.3.2</a>, <a href="#7.5">7.5</a>, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.8.2.4">7.8.2.4</a>,
24351 element type, <a href="#6.2.5">6.2.5</a> <a href="#7.12.1">7.12.1</a>, <a href="#7.14.1.1">7.14.1.1</a>, <a href="#7.19.3">7.19.3</a>, <a href="#7.19.9.3">7.19.9.3</a>, <a href="#7.19.10.4">7.19.10.4</a>,
24352 elif preprocessing directive, <a href="#6.10.1">6.10.1</a> <a href="#7.20.1">7.20.1</a>, <a href="#7.20.1.3">7.20.1.3</a>, <a href="#7.20.1.4">7.20.1.4</a>, <a href="#7.21.6.2">7.21.6.2</a>, <a href="#7.24.3.1">7.24.3.1</a>,
24353 ellipsis punctuator (...), <a href="#6.5.2.2">6.5.2.2</a>, <a href="#6.7.5.3">6.7.5.3</a>, <a href="#6.10.3">6.10.3</a> <a href="#7.24.3.3">7.24.3.3</a>, <a href="#7.24.4.1.1">7.24.4.1.1</a>, <a href="#7.24.4.1.2">7.24.4.1.2</a>, <a href="#7.24.6.3.2">7.24.6.3.2</a>,
24354 else preprocessing directive, <a href="#6.10.1">6.10.1</a> <a href="#7.24.6.3.3">7.24.6.3.3</a>, <a href="#7.24.6.4.1">7.24.6.4.1</a>, <a href="#7.24.6.4.2">7.24.6.4.2</a>, <a href="#J.5.17">J.5.17</a>
24355 else statement, <a href="#6.8.4.1">6.8.4.1</a> errno.h header, <a href="#7.5">7.5</a>, <a href="#7.26.3">7.26.3</a>
24357 encoding error, <a href="#7.19.3">7.19.3</a>, <a href="#7.24.3.1">7.24.3.1</a>, <a href="#7.24.3.3">7.24.3.3</a>, domain, see domain error
24358 <a href="#7.24.6.3.2">7.24.6.3.2</a>, <a href="#7.24.6.3.3">7.24.6.3.3</a>, <a href="#7.24.6.4.1">7.24.6.4.1</a>, <a href="#7.24.6.4.2">7.24.6.4.2</a> encoding, see encoding error
24360 <!--page 538 -->
24361 error conditions, <a href="#7.12.1">7.12.1</a> extended characters, <a href="#5.2.1">5.2.1</a>
24362 error functions, <a href="#7.12.8">7.12.8</a>, <a href="#F.9.5">F.9.5</a> extended integer types, <a href="#6.2.5">6.2.5</a>, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.4.4.1">6.4.4.1</a>,
24363 error indicator, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.5.3">7.19.5.3</a>, <a href="#7.19.7.1">7.19.7.1</a>, <a href="#7.18">7.18</a>
24364 <a href="#7.19.7.3">7.19.7.3</a>, <a href="#7.19.7.5">7.19.7.5</a>, <a href="#7.19.7.6">7.19.7.6</a>, <a href="#7.19.7.8">7.19.7.8</a>, extended multibyte/wide character conversion
24365 <a href="#7.19.7.9">7.19.7.9</a>, <a href="#7.19.9.2">7.19.9.2</a>, <a href="#7.19.10.1">7.19.10.1</a>, <a href="#7.19.10.3">7.19.10.3</a>, utilities, <a href="#7.24.6">7.24.6</a>
24366 <a href="#7.24.3.1">7.24.3.1</a>, <a href="#7.24.3.3">7.24.3.3</a> extensible wide character case mapping functions,
24367 error preprocessing directive, <a href="#4">4</a>, <a href="#6.10.5">6.10.5</a> <a href="#7.25.3.2">7.25.3.2</a>
24368 error-handling functions, <a href="#7.19.10">7.19.10</a>, <a href="#7.21.6.2">7.21.6.2</a> extensible wide character classification functions,
24370 escape sequences, <a href="#5.2.1">5.2.1</a>, <a href="#5.2.2">5.2.2</a>, <a href="#6.4.4.4">6.4.4.4</a>, <a href="#6.11.4">6.11.4</a> extern storage-class specifier, <a href="#6.2.2">6.2.2</a>, <a href="#6.7.1">6.7.1</a>
24371 evaluation format, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.4.4.2">6.4.4.2</a>, <a href="#7.12">7.12</a> external definition, <a href="#6.9">6.9</a>
24372 evaluation method, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.5">6.5</a>, <a href="#F.7.5">F.7.5</a> external identifiers, underscore, <a href="#7.1.3">7.1.3</a>
24374 exceptional condition, <a href="#6.5">6.5</a>, <a href="#7.12.1">7.12.1</a> external name, <a href="#6.4.2.1">6.4.2.1</a>
24375 excess precision, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.3.1.5">6.3.1.5</a>, <a href="#6.3.1.8">6.3.1.8</a>, external object definitions, <a href="#6.9.2">6.9.2</a>
24377 excess range, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.3.1.5">6.3.1.5</a>, <a href="#6.3.1.8">6.3.1.8</a>, <a href="#6.8.6.4">6.8.6.4</a> fabs functions, <a href="#7.12.7.2">7.12.7.2</a>, <a href="#F.9.4.2">F.9.4.2</a>
24378 exclusive OR operators fabs type-generic macro, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</a>
24380 bitwise assignment (^=), <a href="#6.5.16.2">6.5.16.2</a> fclose function, <a href="#7.19.5.1">7.19.5.1</a>
24381 executable program, <a href="#5.1.1.1">5.1.1.1</a> fdim functions, <a href="#7.12.12.1">7.12.12.1</a>, <a href="#F.9.9.1">F.9.9.1</a>
24382 execution character set, <a href="#5.2.1">5.2.1</a> fdim type-generic macro, <a href="#7.22">7.22</a>
24383 execution environment, <a href="#5">5</a>, <a href="#5.1.2">5.1.2</a>, see also FE_ALL_EXCEPT macro, <a href="#7.6">7.6</a>
24385 execution sequence, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#6.8">6.8</a> FE_DIVBYZERO macro, <a href="#7.6">7.6</a>, <a href="#7.12">7.12</a>, <a href="#F.3">F.3</a>
24386 exit function, <a href="#5.1.2.2.3">5.1.2.2.3</a>, <a href="#7.19.3">7.19.3</a>, <a href="#7.20">7.20</a>, <a href="#7.20.4.3">7.20.4.3</a>, FE_DOWNWARD macro, <a href="#7.6">7.6</a>, <a href="#F.3">F.3</a>
24387 <a href="#7.20.4.4">7.20.4.4</a> FE_INEXACT macro, <a href="#7.6">7.6</a>, <a href="#F.3">F.3</a>
24388 EXIT_FAILURE macro, <a href="#7.20">7.20</a>, <a href="#7.20.4.3">7.20.4.3</a> FE_INVALID macro, <a href="#7.6">7.6</a>, <a href="#7.12">7.12</a>, <a href="#F.3">F.3</a>
24389 EXIT_SUCCESS macro, <a href="#7.20">7.20</a>, <a href="#7.20.4.3">7.20.4.3</a> FE_OVERFLOW macro, <a href="#7.6">7.6</a>, <a href="#7.12">7.12</a>, <a href="#F.3">F.3</a>
24390 exp functions, <a href="#7.12.6.1">7.12.6.1</a>, <a href="#F.9.3.1">F.9.3.1</a> FE_TONEAREST macro, <a href="#7.6">7.6</a>, <a href="#F.3">F.3</a>
24391 exp type-generic macro, <a href="#7.22">7.22</a> FE_TOWARDZERO macro, <a href="#7.6">7.6</a>, <a href="#F.3">F.3</a>
24392 exp2 functions, <a href="#7.12.6.2">7.12.6.2</a>, <a href="#F.9.3.2">F.9.3.2</a> FE_UNDERFLOW macro, <a href="#7.6">7.6</a>, <a href="#F.3">F.3</a>
24393 exp2 type-generic macro, <a href="#7.22">7.22</a> FE_UPWARD macro, <a href="#7.6">7.6</a>, <a href="#F.3">F.3</a>
24394 explicit conversion, <a href="#6.3">6.3</a> feclearexcept function, <a href="#7.6.2">7.6.2</a>, <a href="#7.6.2.1">7.6.2.1</a>, <a href="#F.3">F.3</a>
24395 expm1 functions, <a href="#7.12.6.3">7.12.6.3</a>, <a href="#F.9.3.3">F.9.3.3</a> fegetenv function, <a href="#7.6.4.1">7.6.4.1</a>, <a href="#7.6.4.3">7.6.4.3</a>, <a href="#7.6.4.4">7.6.4.4</a>, <a href="#F.3">F.3</a>
24396 expm1 type-generic macro, <a href="#7.22">7.22</a> fegetexceptflag function, <a href="#7.6.2">7.6.2</a>, <a href="#7.6.2.2">7.6.2.2</a>, <a href="#F.3">F.3</a>
24397 exponent part, <a href="#6.4.4.2">6.4.4.2</a> fegetround function, <a href="#7.6">7.6</a>, <a href="#7.6.3.1">7.6.3.1</a>, <a href="#F.3">F.3</a>
24398 exponential functions feholdexcept function, <a href="#7.6.4.2">7.6.4.2</a>, <a href="#7.6.4.3">7.6.4.3</a>,
24399 complex, <a href="#7.3.7">7.3.7</a>, <a href="#G.6.3">G.6.3</a> <a href="#7.6.4.4">7.6.4.4</a>, <a href="#F.3">F.3</a>
24400 real, <a href="#7.12.6">7.12.6</a>, <a href="#F.9.3">F.9.3</a> fenv.h header, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.6">7.6</a>, <a href="#7.12">7.12</a>, <a href="#F">F</a>, <a href="#H">H</a>
24401 expression, <a href="#6.5">6.5</a> FENV_ACCESS pragma, <a href="#6.10.6">6.10.6</a>, <a href="#7.6.1">7.6.1</a>, <a href="#F.7">F.7</a>, <a href="#F.8">F.8</a>,
24405 full, <a href="#6.8">6.8</a> feraiseexcept function, <a href="#7.6.2">7.6.2</a>, <a href="#7.6.2.3">7.6.2.3</a>, <a href="#F.3">F.3</a>
24406 order of evaluation, <a href="#6.5">6.5</a> ferror function, <a href="#7.19.10.3">7.19.10.3</a>
24407 parenthesized, <a href="#6.5.1">6.5.1</a> fesetenv function, <a href="#7.6.4.3">7.6.4.3</a>, <a href="#F.3">F.3</a>
24408 primary, <a href="#6.5.1">6.5.1</a> fesetexceptflag function, <a href="#7.6.2">7.6.2</a>, <a href="#7.6.2.4">7.6.2.4</a>, <a href="#F.3">F.3</a>
24409 unary, <a href="#6.5.3">6.5.3</a> fesetround function, <a href="#7.6">7.6</a>, <a href="#7.6.3.2">7.6.3.2</a>, <a href="#F.3">F.3</a>
24410 expression statement, <a href="#6.8.3">6.8.3</a> fetestexcept function, <a href="#7.6.2">7.6.2</a>, <a href="#7.6.2.5">7.6.2.5</a>, <a href="#F.3">F.3</a>
24411 extended character set, <a href="#3.7.2">3.7.2</a>, <a href="#5.2.1">5.2.1</a>, <a href="#5.2.1.2">5.2.1.2</a> feupdateenv function, <a href="#7.6.4.2">7.6.4.2</a>, <a href="#7.6.4.4">7.6.4.4</a>, <a href="#F.3">F.3</a>
24412 <!--page 539 -->
24413 fexcept_t type, <a href="#7.6">7.6</a>, <a href="#F.3">F.3</a> floating-point status flag, <a href="#7.6">7.6</a>, <a href="#F.7.6">F.7.6</a>
24414 fflush function, <a href="#7.19.5.2">7.19.5.2</a>, <a href="#7.19.5.3">7.19.5.3</a> floor functions, <a href="#7.12.9.2">7.12.9.2</a>, <a href="#F.9.6.2">F.9.6.2</a>
24415 fgetc function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.3">7.19.3</a>, <a href="#7.19.7.1">7.19.7.1</a>, floor type-generic macro, <a href="#7.22">7.22</a>
24416 <a href="#7.19.7.5">7.19.7.5</a>, <a href="#7.19.8.1">7.19.8.1</a> FLT_DIG macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
24417 fgetpos function, <a href="#7.19.2">7.19.2</a>, <a href="#7.19.9.1">7.19.9.1</a>, <a href="#7.19.9.3">7.19.9.3</a> FLT_EPSILON macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
24418 fgets function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.7.2">7.19.7.2</a> FLT_EVAL_METHOD macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.8.6.4">6.8.6.4</a>,
24419 fgetwc function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.3">7.19.3</a>, <a href="#7.24.3.1">7.24.3.1</a>, <a href="#7.12">7.12</a>
24421 fgetws function, <a href="#7.19.1">7.19.1</a>, <a href="#7.24.3.2">7.24.3.2</a> FLT_MAX macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
24422 field width, <a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.24.2.1">7.24.2.1</a> FLT_MAX_10_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
24424 access functions, <a href="#7.19.5">7.19.5</a> FLT_MIN macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
24426 operations, <a href="#7.19.4">7.19.4</a> FLT_MIN_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>
24427 position indicator, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.2">7.19.2</a>, <a href="#7.19.3">7.19.3</a>, FLT_RADIX macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.20.1.3">7.20.1.3</a>,
24428 <a href="#7.19.5.3">7.19.5.3</a>, <a href="#7.19.7.1">7.19.7.1</a>, <a href="#7.19.7.3">7.19.7.3</a>, <a href="#7.19.7.11">7.19.7.11</a>, <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.4.1.1">7.24.4.1.1</a>
24429 <a href="#7.19.8.1">7.19.8.1</a>, <a href="#7.19.8.2">7.19.8.2</a>, <a href="#7.19.9.1">7.19.9.1</a>, <a href="#7.19.9.2">7.19.9.2</a>, FLT_ROUNDS macro, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.6">7.6</a>, <a href="#F.3">F.3</a>
24430 <a href="#7.19.9.3">7.19.9.3</a>, <a href="#7.19.9.4">7.19.9.4</a>, <a href="#7.19.9.5">7.19.9.5</a>, <a href="#7.24.3.1">7.24.3.1</a>, fma functions, <a href="#7.12">7.12</a>, <a href="#7.12.13.1">7.12.13.1</a>, <a href="#F.9.10.1">F.9.10.1</a>
24431 <a href="#7.24.3.3">7.24.3.3</a>, <a href="#7.24.3.10">7.24.3.10</a> fma type-generic macro, <a href="#7.22">7.22</a>
24432 positioning functions, <a href="#7.19.9">7.19.9</a> fmax functions, <a href="#7.12.12.2">7.12.12.2</a>, <a href="#F.9.9.2">F.9.9.2</a>
24433 file scope, <a href="#6.2.1">6.2.1</a>, <a href="#6.9">6.9</a> fmax type-generic macro, <a href="#7.22">7.22</a>
24434 FILE type, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.3">7.19.3</a> fmin functions, <a href="#7.12.12.3">7.12.12.3</a>, <a href="#F.9.9.3">F.9.9.3</a>
24435 FILENAME_MAX macro, <a href="#7.19.1">7.19.1</a> fmin type-generic macro, <a href="#7.22">7.22</a>
24436 flags, <a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.24.2.1">7.24.2.1</a> fmod functions, <a href="#7.12.10.1">7.12.10.1</a>, <a href="#F.9.7.1">F.9.7.1</a>
24437 floating-point status, see floating-point status fmod type-generic macro, <a href="#7.22">7.22</a>
24439 flexible array member, <a href="#6.7.2.1">6.7.2.1</a> FOPEN_MAX macro, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.3">7.19.3</a>, <a href="#7.19.4.3">7.19.4.3</a>
24440 float _Complex type, <a href="#6.2.5">6.2.5</a> for statement, <a href="#6.8.5">6.8.5</a>, <a href="#6.8.5.3">6.8.5.3</a>
24441 float _Complex type conversion, <a href="#6.3.1.6">6.3.1.6</a>, form-feed character, <a href="#5.2.1">5.2.1</a>, <a href="#6.4">6.4</a>
24442 <a href="#6.3.1.7">6.3.1.7</a>, <a href="#6.3.1.8">6.3.1.8</a> form-feed escape sequence (\f), <a href="#5.2.2">5.2.2</a>, <a href="#6.4.4.4">6.4.4.4</a>,
24444 float type, <a href="#6.2.5">6.2.5</a>, <a href="#6.4.4.2">6.4.4.2</a>, <a href="#6.7.2">6.7.2</a>, <a href="#F.2">F.2</a> formal argument (deprecated), <a href="#3.15">3.15</a>
24445 float type conversion, <a href="#6.3.1.4">6.3.1.4</a>, <a href="#6.3.1.5">6.3.1.5</a>, <a href="#6.3.1.7">6.3.1.7</a>, formal parameter, <a href="#3.15">3.15</a>
24446 <a href="#6.3.1.8">6.3.1.8</a> formatted input/output functions, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.19.6">7.19.6</a>
24447 float.h header, <a href="#4">4</a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.7">7.7</a>, <a href="#7.20.1.3">7.20.1.3</a>, wide character, <a href="#7.24.2">7.24.2</a>
24449 float_t type, <a href="#7.12">7.12</a>, <a href="#J.5.6">J.5.6</a> forward reference, <a href="#3.11">3.11</a>
24450 floating constant, <a href="#6.4.4.2">6.4.4.2</a> FP_CONTRACT pragma, <a href="#6.5">6.5</a>, <a href="#6.10.6">6.10.6</a>, <a href="#7.12.2">7.12.2</a>, see
24451 floating suffix, f or <a href="#F">F</a>, <a href="#6.4.4.2">6.4.4.2</a> also contracted expression
24452 floating type conversion, <a href="#6.3.1.4">6.3.1.4</a>, <a href="#6.3.1.5">6.3.1.5</a>, <a href="#6.3.1.7">6.3.1.7</a>, FP_FAST_FMA macro, <a href="#7.12">7.12</a>
24454 floating types, <a href="#6.2.5">6.2.5</a>, <a href="#6.11.1">6.11.1</a> FP_FAST_FMAL macro, <a href="#7.12">7.12</a>
24455 floating-point accuracy, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.4.4.2">6.4.4.2</a>, <a href="#6.5">6.5</a>, FP_ILOGB0 macro, <a href="#7.12">7.12</a>, <a href="#7.12.6.5">7.12.6.5</a>
24456 <a href="#7.20.1.3">7.20.1.3</a>, <a href="#F.5">F.5</a>, see also contracted expression FP_ILOGBNAN macro, <a href="#7.12">7.12</a>, <a href="#7.12.6.5">7.12.6.5</a>
24457 floating-point arithmetic functions, <a href="#7.12">7.12</a>, <a href="#F.9">F.9</a> FP_INFINITE macro, <a href="#7.12">7.12</a>, <a href="#F.3">F.3</a>
24458 floating-point classification functions, <a href="#7.12.3">7.12.3</a> FP_NAN macro, <a href="#7.12">7.12</a>, <a href="#F.3">F.3</a>
24459 floating-point control mode, <a href="#7.6">7.6</a>, <a href="#F.7.6">F.7.6</a> FP_NORMAL macro, <a href="#7.12">7.12</a>, <a href="#F.3">F.3</a>
24460 floating-point environment, <a href="#7.6">7.6</a>, <a href="#F.7">F.7</a>, <a href="#F.7.6">F.7.6</a> FP_SUBNORMAL macro, <a href="#7.12">7.12</a>, <a href="#F.3">F.3</a>
24461 floating-point exception, <a href="#7.6">7.6</a>, <a href="#7.6.2">7.6.2</a>, <a href="#F.9">F.9</a> FP_ZERO macro, <a href="#7.12">7.12</a>, <a href="#F.3">F.3</a>
24462 floating-point number, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.2.5">6.2.5</a> fpclassify macro, <a href="#7.12.3.1">7.12.3.1</a>, <a href="#F.3">F.3</a>
24463 floating-point rounding mode, <a href="#5.2.4.2.2">5.2.4.2.2</a> fpos_t type, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.2">7.19.2</a>
24464 <!--page 540 -->
24465 fprintf function, <a href="#7.8.1">7.8.1</a>, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.6.1">7.19.6.1</a>, language, <a href="#6.11">6.11</a>
24466 <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.19.6.3">7.19.6.3</a>, <a href="#7.19.6.5">7.19.6.5</a>, <a href="#7.19.6.6">7.19.6.6</a>, library, <a href="#7.26">7.26</a>
24467 <a href="#7.19.6.8">7.19.6.8</a>, <a href="#7.24.2.2">7.24.2.2</a>, <a href="#F.3">F.3</a> fwide function, <a href="#7.19.2">7.19.2</a>, <a href="#7.24.3.5">7.24.3.5</a>
24468 fputc function, <a href="#5.2.2">5.2.2</a>, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.3">7.19.3</a>, <a href="#7.19.7.3">7.19.7.3</a>, fwprintf function, <a href="#7.8.1">7.8.1</a>, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.6.2">7.19.6.2</a>,
24469 <a href="#7.19.7.8">7.19.7.8</a>, <a href="#7.19.8.2">7.19.8.2</a> <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a>, <a href="#7.24.2.3">7.24.2.3</a>, <a href="#7.24.2.5">7.24.2.5</a>,
24470 fputs function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.7.4">7.19.7.4</a> <a href="#7.24.2.11">7.24.2.11</a>
24471 fputwc function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.3">7.19.3</a>, <a href="#7.24.3.3">7.24.3.3</a>, fwrite function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.8.2">7.19.8.2</a>
24472 <a href="#7.24.3.8">7.24.3.8</a> fwscanf function, <a href="#7.8.1">7.8.1</a>, <a href="#7.19.1">7.19.1</a>, <a href="#7.24.2.2">7.24.2.2</a>,
24473 fputws function, <a href="#7.19.1">7.19.1</a>, <a href="#7.24.3.4">7.24.3.4</a> <a href="#7.24.2.4">7.24.2.4</a>, <a href="#7.24.2.6">7.24.2.6</a>, <a href="#7.24.2.12">7.24.2.12</a>, <a href="#7.24.3.10">7.24.3.10</a>
24475 free function, <a href="#7.20.3.2">7.20.3.2</a>, <a href="#7.20.3.4">7.20.3.4</a> gamma functions, <a href="#7.12.8">7.12.8</a>, <a href="#F.9.5">F.9.5</a>
24476 freestanding execution environment, <a href="#4">4</a>, <a href="#5.1.2">5.1.2</a>, general utilities, <a href="#7.20">7.20</a>
24478 freopen function, <a href="#7.19.2">7.19.2</a>, <a href="#7.19.5.4">7.19.5.4</a> general wide string utilities, <a href="#7.24.4">7.24.4</a>
24479 frexp functions, <a href="#7.12.6.4">7.12.6.4</a>, <a href="#F.9.3.4">F.9.3.4</a> generic parameters, <a href="#7.22">7.22</a>
24480 frexp type-generic macro, <a href="#7.22">7.22</a> getc function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.7.5">7.19.7.5</a>, <a href="#7.19.7.6">7.19.7.6</a>
24481 fscanf function, <a href="#7.8.1">7.8.1</a>, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.6.2">7.19.6.2</a>, getchar function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.7.6">7.19.7.6</a>
24482 <a href="#7.19.6.4">7.19.6.4</a>, <a href="#7.19.6.7">7.19.6.7</a>, <a href="#7.19.6.9">7.19.6.9</a>, <a href="#F.3">F.3</a> getenv function, <a href="#7.20.4.5">7.20.4.5</a>
24483 fseek function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.5.3">7.19.5.3</a>, <a href="#7.19.7.11">7.19.7.11</a>, gets function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.7.7">7.19.7.7</a>, <a href="#7.26.9">7.26.9</a>
24484 <a href="#7.19.9.2">7.19.9.2</a>, <a href="#7.19.9.4">7.19.9.4</a>, <a href="#7.19.9.5">7.19.9.5</a>, <a href="#7.24.3.10">7.24.3.10</a> getwc function, <a href="#7.19.1">7.19.1</a>, <a href="#7.24.3.6">7.24.3.6</a>, <a href="#7.24.3.7">7.24.3.7</a>
24485 fsetpos function, <a href="#7.19.2">7.19.2</a>, <a href="#7.19.5.3">7.19.5.3</a>, <a href="#7.19.7.11">7.19.7.11</a>, getwchar function, <a href="#7.19.1">7.19.1</a>, <a href="#7.24.3.7">7.24.3.7</a>
24486 <a href="#7.19.9.1">7.19.9.1</a>, <a href="#7.19.9.3">7.19.9.3</a>, <a href="#7.24.3.10">7.24.3.10</a> gmtime function, <a href="#7.23.3.3">7.23.3.3</a>
24487 ftell function, <a href="#7.19.9.2">7.19.9.2</a>, <a href="#7.19.9.4">7.19.9.4</a> goto statement, <a href="#6.2.1">6.2.1</a>, <a href="#6.8.1">6.8.1</a>, <a href="#6.8.6.1">6.8.6.1</a>
24489 full expression, <a href="#6.8">6.8</a> greater-than operator (>), <a href="#6.5.8">6.5.8</a>
24490 fully buffered stream, <a href="#7.19.3">7.19.3</a> greater-than-or-equal-to operator (>=), <a href="#6.5.8">6.5.8</a>
24491 function
24492 argument, <a href="#6.5.2.2">6.5.2.2</a>, <a href="#6.9.1">6.9.1</a> header, <a href="#5.1.1.1">5.1.1.1</a>, <a href="#7.1.2">7.1.2</a>, see also standard headers
24493 body, <a href="#6.9.1">6.9.1</a> header names, <a href="#6.4">6.4</a>, <a href="#6.4.7">6.4.7</a>, <a href="#6.10.2">6.10.2</a>
24495 library, <a href="#7.1.4">7.1.4</a> hexadecimal digit, <a href="#6.4.4.1">6.4.4.1</a>, <a href="#6.4.4.2">6.4.4.2</a>, <a href="#6.4.4.4">6.4.4.4</a>
24496 declarator, <a href="#6.7.5.3">6.7.5.3</a>, <a href="#6.11.6">6.11.6</a> hexadecimal prefix, <a href="#6.4.4.1">6.4.4.1</a>
24497 definition, <a href="#6.7.5.3">6.7.5.3</a>, <a href="#6.9.1">6.9.1</a>, <a href="#6.11.7">6.11.7</a> hexadecimal-character escape sequence
24498 designator, <a href="#6.3.2.1">6.3.2.1</a> (\x hexadecimal digits), <a href="#6.4.4.4">6.4.4.4</a>
24500 library, <a href="#5.1.1.1">5.1.1.1</a>, <a href="#7.1.4">7.1.4</a> horizontal-tab character, <a href="#5.2.1">5.2.1</a>, <a href="#6.4">6.4</a>
24501 name length, <a href="#5.2.4.1">5.2.4.1</a>, <a href="#6.4.2.1">6.4.2.1</a>, <a href="#6.11.3">6.11.3</a> horizontal-tab escape sequence (\r), <a href="#7.25.2.1.3">7.25.2.1.3</a>
24502 parameter, <a href="#5.1.2.2.1">5.1.2.2.1</a>, <a href="#6.5.2.2">6.5.2.2</a>, <a href="#6.7">6.7</a>, <a href="#6.9.1">6.9.1</a> horizontal-tab escape sequence (\t), <a href="#5.2.2">5.2.2</a>,
24503 prototype, <a href="#5.1.2.2.1">5.1.2.2.1</a>, <a href="#6.2.1">6.2.1</a>, <a href="#6.2.7">6.2.7</a>, <a href="#6.5.2.2">6.5.2.2</a>, <a href="#6.7">6.7</a>, <a href="#6.4.4.4">6.4.4.4</a>, <a href="#7.4.1.3">7.4.1.3</a>, <a href="#7.4.1.10">7.4.1.10</a>
24504 <a href="#6.7.5.3">6.7.5.3</a>, <a href="#6.9.1">6.9.1</a>, <a href="#6.11.6">6.11.6</a>, <a href="#6.11.7">6.11.7</a>, <a href="#7.1.2">7.1.2</a>, <a href="#7.12">7.12</a> hosted execution environment, <a href="#4">4</a>, <a href="#5.1.2">5.1.2</a>, <a href="#5.1.2.2">5.1.2.2</a>
24505 prototype scope, <a href="#6.2.1">6.2.1</a>, <a href="#6.7.5.2">6.7.5.2</a> HUGE_VAL macro, <a href="#7.12">7.12</a>, <a href="#7.12.1">7.12.1</a>, <a href="#7.20.1.3">7.20.1.3</a>,
24506 recursive call, <a href="#6.5.2.2">6.5.2.2</a> <a href="#7.24.4.1.1">7.24.4.1.1</a>, <a href="#F.9">F.9</a>
24507 return, <a href="#6.8.6.4">6.8.6.4</a> HUGE_VALF macro, <a href="#7.12">7.12</a>, <a href="#7.12.1">7.12.1</a>, <a href="#7.20.1.3">7.20.1.3</a>,
24508 scope, <a href="#6.2.1">6.2.1</a> <a href="#7.24.4.1.1">7.24.4.1.1</a>, <a href="#F.9">F.9</a>
24509 type, <a href="#6.2.5">6.2.5</a> HUGE_VALL macro, <a href="#7.12">7.12</a>, <a href="#7.12.1">7.12.1</a>, <a href="#7.20.1.3">7.20.1.3</a>,
24510 type conversion, <a href="#6.3.2.1">6.3.2.1</a> <a href="#7.24.4.1.1">7.24.4.1.1</a>, <a href="#F.9">F.9</a>
24512 function type, <a href="#6.2.5">6.2.5</a> complex, <a href="#7.3.6">7.3.6</a>, <a href="#G.6.2">G.6.2</a>
24513 function-call operator (( )), <a href="#6.5.2.2">6.5.2.2</a> real, <a href="#7.12.5">7.12.5</a>, <a href="#F.9.2">F.9.2</a>
24514 function-like macro, <a href="#6.10.3">6.10.3</a> hypot functions, <a href="#7.12.7.3">7.12.7.3</a>, <a href="#F.9.4.3">F.9.4.3</a>
24516 <!--page 541 -->
24517 <a href="#I">I</a> macro, <a href="#7.3.1">7.3.1</a>, <a href="#7.3.9.4">7.3.9.4</a>, <a href="#G.6">G.6</a> initial position, <a href="#5.2.2">5.2.2</a>
24518 identifier, <a href="#6.4.2.1">6.4.2.1</a>, <a href="#6.5.1">6.5.1</a> initial shift state, <a href="#5.2.1.2">5.2.1.2</a>
24519 linkage, see linkage initialization, <a href="#5.1.2">5.1.2</a>, <a href="#6.2.4">6.2.4</a>, <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.2.5">6.5.2.5</a>, <a href="#6.7.8">6.7.8</a>,
24522 reserved, <a href="#6.4.1">6.4.1</a>, <a href="#7.1.3">7.1.3</a> initializer, <a href="#6.7.8">6.7.8</a>
24527 IEC 559, <a href="#F.1">F.1</a> input failure, <a href="#7.24.2.6">7.24.2.6</a>, <a href="#7.24.2.8">7.24.2.8</a>, <a href="#7.24.2.10">7.24.2.10</a>
24528 IEC 60559, <a href="#2">2</a>, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.10.8">6.10.8</a>, <a href="#7.3.3">7.3.3</a>, <a href="#7.6">7.6</a>, input/output functions
24529 <a href="#7.6.4.2">7.6.4.2</a>, <a href="#7.12.1">7.12.1</a>, <a href="#7.12.10.2">7.12.10.2</a>, <a href="#7.12.14">7.12.14</a>, <a href="#F">F</a>, <a href="#G">G</a>, <a href="#H.1">H.1</a> character, <a href="#7.19.7">7.19.7</a>
24535 if preprocessing directive, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, input/output header, <a href="#7.19">7.19</a>
24536 <a href="#6.10.1">6.10.1</a>, <a href="#7.1.4">7.1.4</a> input/output, device, <a href="#5.1.2.3">5.1.2.3</a>
24537 if statement, <a href="#6.8.4.1">6.8.4.1</a> int type, <a href="#6.2.5">6.2.5</a>, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.3.1.3">6.3.1.3</a>, <a href="#6.4.4.1">6.4.4.1</a>, <a href="#6.7.2">6.7.2</a>
24538 ifdef preprocessing directive, <a href="#6.10.1">6.10.1</a> int type conversion, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.3.1.3">6.3.1.3</a>, <a href="#6.3.1.4">6.3.1.4</a>,
24540 ilogb functions, <a href="#7.12">7.12</a>, <a href="#7.12.6.5">7.12.6.5</a>, <a href="#F.9.3.5">F.9.3.5</a> INT_FASTN_MAX macros, <a href="#7.18.2.3">7.18.2.3</a>
24541 ilogb type-generic macro, <a href="#7.22">7.22</a> INT_FASTN_MIN macros, <a href="#7.18.2.3">7.18.2.3</a>
24542 imaginary macro, <a href="#7.3.1">7.3.1</a>, <a href="#G.6">G.6</a> int_fastN_t types, <a href="#7.18.1.3">7.18.1.3</a>
24544 imaginary type domain, <a href="#G.2">G.2</a> INT_LEASTN_MIN macros, <a href="#7.18.2.2">7.18.2.2</a>
24546 imaxabs function, <a href="#7.8.2.1">7.8.2.1</a> INT_MAX macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#7.12">7.12</a>, <a href="#7.12.6.5">7.12.6.5</a>
24547 imaxdiv function, <a href="#7.8">7.8</a>, <a href="#7.8.2.2">7.8.2.2</a> INT_MIN macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#7.12">7.12</a>
24548 imaxdiv_t type, <a href="#7.8">7.8</a> integer arithmetic functions, <a href="#7.8.2.1">7.8.2.1</a>, <a href="#7.8.2.2">7.8.2.2</a>,
24550 implementation limit, <a href="#3.13">3.13</a>, <a href="#4">4</a>, <a href="#5.2.4.2">5.2.4.2</a>, <a href="#6.4.2.1">6.4.2.1</a>, integer character constant, <a href="#6.4.4.4">6.4.4.4</a>
24551 <a href="#6.7.5">6.7.5</a>, <a href="#6.8.4.2">6.8.4.2</a>, <a href="#E">E</a>, see also environmental integer constant, <a href="#6.4.4.1">6.4.4.1</a>
24553 implementation-defined behavior, <a href="#3.4.1">3.4.1</a>, <a href="#4">4</a>, <a href="#J.3">J.3</a> integer conversion rank, <a href="#6.3.1.1">6.3.1.1</a>
24554 implementation-defined value, <a href="#3.17.1">3.17.1</a> integer promotions, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#6.3.1.1">6.3.1.1</a>,
24555 implicit conversion, <a href="#6.3">6.3</a> <a href="#6.5.2.2">6.5.2.2</a>, <a href="#6.5.3.3">6.5.3.3</a>, <a href="#6.5.7">6.5.7</a>, <a href="#6.8.4.2">6.8.4.2</a>, <a href="#7.18.2">7.18.2</a>, <a href="#7.18.3">7.18.3</a>,
24556 implicit initialization, <a href="#6.7.8">6.7.8</a> <a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.24.2.1">7.24.2.1</a>
24557 include preprocessing directive, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#6.10.2">6.10.2</a> integer suffix, <a href="#6.4.4.1">6.4.4.1</a>
24558 inclusive OR operators integer type conversion, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.3.1.3">6.3.1.3</a>, <a href="#6.3.1.4">6.3.1.4</a>,
24560 bitwise assignment (|=), <a href="#6.5.16.2">6.5.16.2</a> integer types, <a href="#6.2.5">6.2.5</a>, <a href="#7.18">7.18</a>
24561 incomplete type, <a href="#6.2.5">6.2.5</a> extended, <a href="#6.2.5">6.2.5</a>, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.4.4.1">6.4.4.1</a>, <a href="#7.18">7.18</a>
24562 increment operators, see arithmetic operators, interactive device, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#7.19.3">7.19.3</a>, <a href="#7.19.5.3">7.19.5.3</a>
24564 indeterminate value, <a href="#3.17.2">3.17.2</a> internal name, <a href="#6.4.2.1">6.4.2.1</a>
24565 indirection operator (*), <a href="#6.5.2.1">6.5.2.1</a>, <a href="#6.5.3.2">6.5.3.2</a> interrupt, <a href="#5.2.3">5.2.3</a>
24566 inequality operator (!=), <a href="#6.5.9">6.5.9</a> INTMAX_C macro, <a href="#7.18.4.2">7.18.4.2</a>
24567 INFINITY macro, <a href="#7.3.9.4">7.3.9.4</a>, <a href="#7.12">7.12</a>, <a href="#F.2.1">F.2.1</a> INTMAX_MAX macro, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.8.2.4">7.8.2.4</a>, <a href="#7.18.2.5">7.18.2.5</a>
24568 <!--page 542 -->
24569 INTMAX_MIN macro, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.8.2.4">7.8.2.4</a>, <a href="#7.18.2.5">7.18.2.5</a> iswalpha function, <a href="#7.25.2.1.1">7.25.2.1.1</a>, <a href="#7.25.2.1.2">7.25.2.1.2</a>,
24570 intmax_t type, <a href="#7.18.1.5">7.18.1.5</a>, <a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.25.2.2.1">7.25.2.2.1</a>
24571 <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a> iswblank function, <a href="#7.25.2.1.3">7.25.2.1.3</a>, <a href="#7.25.2.2.1">7.25.2.2.1</a>
24572 INTN_C macros, <a href="#7.18.4.1">7.18.4.1</a> iswcntrl function, <a href="#7.25.2.1.2">7.25.2.1.2</a>, <a href="#7.25.2.1.4">7.25.2.1.4</a>,
24573 INTN_MAX macros, <a href="#7.18.2.1">7.18.2.1</a> <a href="#7.25.2.1.7">7.25.2.1.7</a>, <a href="#7.25.2.1.11">7.25.2.1.11</a>, <a href="#7.25.2.2.1">7.25.2.2.1</a>
24574 INTN_MIN macros, <a href="#7.18.2.1">7.18.2.1</a> iswctype function, <a href="#7.25.2.2.1">7.25.2.2.1</a>, <a href="#7.25.2.2.2">7.25.2.2.2</a>
24575 intN_t types, <a href="#7.18.1.1">7.18.1.1</a> iswdigit function, <a href="#7.25.2.1.1">7.25.2.1.1</a>, <a href="#7.25.2.1.2">7.25.2.1.2</a>,
24576 INTPTR_MAX macro, <a href="#7.18.2.4">7.18.2.4</a> <a href="#7.25.2.1.5">7.25.2.1.5</a>, <a href="#7.25.2.1.7">7.25.2.1.7</a>, <a href="#7.25.2.1.11">7.25.2.1.11</a>, <a href="#7.25.2.2.1">7.25.2.2.1</a>
24577 INTPTR_MIN macro, <a href="#7.18.2.4">7.18.2.4</a> iswgraph function, <a href="#7.25.2.1">7.25.2.1</a>, <a href="#7.25.2.1.6">7.25.2.1.6</a>,
24578 intptr_t type, <a href="#7.18.1.4">7.18.1.4</a> <a href="#7.25.2.1.10">7.25.2.1.10</a>, <a href="#7.25.2.2.1">7.25.2.2.1</a>
24579 inttypes.h header, <a href="#7.8">7.8</a>, <a href="#7.26.4">7.26.4</a> iswlower function, <a href="#7.25.2.1.2">7.25.2.1.2</a>, <a href="#7.25.2.1.7">7.25.2.1.7</a>,
24580 isalnum function, <a href="#7.4.1.1">7.4.1.1</a>, <a href="#7.4.1.9">7.4.1.9</a>, <a href="#7.4.1.10">7.4.1.10</a> <a href="#7.25.2.2.1">7.25.2.2.1</a>, <a href="#7.25.3.1.1">7.25.3.1.1</a>, <a href="#7.25.3.1.2">7.25.3.1.2</a>
24581 isalpha function, <a href="#7.4.1.1">7.4.1.1</a>, <a href="#7.4.1.2">7.4.1.2</a> iswprint function, <a href="#7.25.2.1.6">7.25.2.1.6</a>, <a href="#7.25.2.1.8">7.25.2.1.8</a>,
24583 iscntrl function, <a href="#7.4.1.2">7.4.1.2</a>, <a href="#7.4.1.4">7.4.1.4</a>, <a href="#7.4.1.7">7.4.1.7</a>, iswpunct function, <a href="#7.25.2.1">7.25.2.1</a>, <a href="#7.25.2.1.2">7.25.2.1.2</a>,
24584 <a href="#7.4.1.11">7.4.1.11</a> <a href="#7.25.2.1.7">7.25.2.1.7</a>, <a href="#7.25.2.1.9">7.25.2.1.9</a>, <a href="#7.25.2.1.10">7.25.2.1.10</a>,
24585 isdigit function, <a href="#7.4.1.1">7.4.1.1</a>, <a href="#7.4.1.2">7.4.1.2</a>, <a href="#7.4.1.5">7.4.1.5</a>, <a href="#7.25.2.1.11">7.25.2.1.11</a>, <a href="#7.25.2.2.1">7.25.2.2.1</a>
24586 <a href="#7.4.1.7">7.4.1.7</a>, <a href="#7.4.1.11">7.4.1.11</a>, <a href="#7.11.1.1">7.11.1.1</a> iswspace function, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.2">7.24.2.2</a>,
24587 isfinite macro, <a href="#7.12.3.2">7.12.3.2</a>, <a href="#F.3">F.3</a> <a href="#7.24.4.1.1">7.24.4.1.1</a>, <a href="#7.24.4.1.2">7.24.4.1.2</a>, <a href="#7.25.2.1.2">7.25.2.1.2</a>, <a href="#7.25.2.1.6">7.25.2.1.6</a>,
24588 isgraph function, <a href="#7.4.1.6">7.4.1.6</a> <a href="#7.25.2.1.7">7.25.2.1.7</a>, <a href="#7.25.2.1.9">7.25.2.1.9</a>, <a href="#7.25.2.1.10">7.25.2.1.10</a>,
24589 isgreater macro, <a href="#7.12.14.1">7.12.14.1</a>, <a href="#F.3">F.3</a> <a href="#7.25.2.1.11">7.25.2.1.11</a>, <a href="#7.25.2.2.1">7.25.2.2.1</a>
24590 isgreaterequal macro, <a href="#7.12.14.2">7.12.14.2</a>, <a href="#F.3">F.3</a> iswupper function, <a href="#7.25.2.1.2">7.25.2.1.2</a>, <a href="#7.25.2.1.11">7.25.2.1.11</a>,
24591 isinf macro, <a href="#7.12.3.3">7.12.3.3</a> <a href="#7.25.2.2.1">7.25.2.2.1</a>, <a href="#7.25.3.1.1">7.25.3.1.1</a>, <a href="#7.25.3.1.2">7.25.3.1.2</a>
24592 isless macro, <a href="#7.12.14.3">7.12.14.3</a>, <a href="#F.3">F.3</a> iswxdigit function, <a href="#7.25.2.1.12">7.25.2.1.12</a>, <a href="#7.25.2.2.1">7.25.2.2.1</a>
24593 islessequal macro, <a href="#7.12.14.4">7.12.14.4</a>, <a href="#F.3">F.3</a> isxdigit function, <a href="#7.4.1.12">7.4.1.12</a>, <a href="#7.11.1.1">7.11.1.1</a>
24594 islessgreater macro, <a href="#7.12.14.5">7.12.14.5</a>, <a href="#F.3">F.3</a> italic type convention, <a href="#3">3</a>, <a href="#6.1">6.1</a>
24595 islower function, <a href="#7.4.1.2">7.4.1.2</a>, <a href="#7.4.1.7">7.4.1.7</a>, <a href="#7.4.2.1">7.4.2.1</a>, iteration statements, <a href="#6.8.5">6.8.5</a>
24597 isnan macro, <a href="#7.12.3.4">7.12.3.4</a>, <a href="#F.3">F.3</a> jmp_buf type, <a href="#7.13">7.13</a>
24600 ISO 4217, <a href="#2">2</a>, <a href="#7.11.2.1">7.11.2.1</a> keywords, <a href="#6.4.1">6.4.1</a>, <a href="#G.2">G.2</a>, <a href="#J.5.9">J.5.9</a>, <a href="#J.5.10">J.5.10</a>
24601 ISO 8601, <a href="#2">2</a>, <a href="#7.23.3.5">7.23.3.5</a> known constant size, <a href="#6.2.5">6.2.5</a>
24602 ISO/IEC 10646, <a href="#2">2</a>, <a href="#6.4.2.1">6.4.2.1</a>, <a href="#6.4.3">6.4.3</a>, <a href="#6.10.8">6.10.8</a>
24603 ISO/IEC 10976-1, <a href="#H.1">H.1</a> L_tmpnam macro, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.4.4">7.19.4.4</a>
24604 ISO/IEC 2382-1, <a href="#2">2</a>, <a href="#3">3</a> label name, <a href="#6.2.1">6.2.1</a>, <a href="#6.2.3">6.2.3</a>
24605 ISO/IEC 646, <a href="#2">2</a>, <a href="#5.2.1.1">5.2.1.1</a> labeled statement, <a href="#6.8.1">6.8.1</a>
24608 iso646.h header, <a href="#4">4</a>, <a href="#7.9">7.9</a> future directions, <a href="#6.11">6.11</a>
24609 isprint function, <a href="#5.2.2">5.2.2</a>, <a href="#7.4.1.8">7.4.1.8</a> syntax summary, <a href="#A">A</a>
24610 ispunct function, <a href="#7.4.1.2">7.4.1.2</a>, <a href="#7.4.1.7">7.4.1.7</a>, <a href="#7.4.1.9">7.4.1.9</a>, Latin alphabet, <a href="#5.2.1">5.2.1</a>, <a href="#6.4.2.1">6.4.2.1</a>
24611 <a href="#7.4.1.11">7.4.1.11</a> LC_ALL macro, <a href="#7.11">7.11</a>, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.11.2.1">7.11.2.1</a>
24612 isspace function, <a href="#7.4.1.2">7.4.1.2</a>, <a href="#7.4.1.7">7.4.1.7</a>, <a href="#7.4.1.9">7.4.1.9</a>, LC_COLLATE macro, <a href="#7.11">7.11</a>, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.21.4.3">7.21.4.3</a>,
24613 <a href="#7.4.1.10">7.4.1.10</a>, <a href="#7.4.1.11">7.4.1.11</a>, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.20.1.3">7.20.1.3</a>, <a href="#7.24.4.4.2">7.24.4.4.2</a>
24614 <a href="#7.20.1.4">7.20.1.4</a>, <a href="#7.24.2.2">7.24.2.2</a> LC_CTYPE macro, <a href="#7.11">7.11</a>, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.20">7.20</a>, <a href="#7.20.7">7.20.7</a>,
24615 isunordered macro, <a href="#7.12.14.6">7.12.14.6</a>, <a href="#F.3">F.3</a> <a href="#7.20.8">7.20.8</a>, <a href="#7.24.6">7.24.6</a>, <a href="#7.25.1">7.25.1</a>, <a href="#7.25.2.2.1">7.25.2.2.1</a>, <a href="#7.25.2.2.2">7.25.2.2.2</a>,
24616 isupper function, <a href="#7.4.1.2">7.4.1.2</a>, <a href="#7.4.1.11">7.4.1.11</a>, <a href="#7.4.2.1">7.4.2.1</a>, <a href="#7.25.3.2.1">7.25.3.2.1</a>, <a href="#7.25.3.2.2">7.25.3.2.2</a>
24617 <a href="#7.4.2.2">7.4.2.2</a> LC_MONETARY macro, <a href="#7.11">7.11</a>, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.11.2.1">7.11.2.1</a>
24618 iswalnum function, <a href="#7.25.2.1.1">7.25.2.1.1</a>, <a href="#7.25.2.1.9">7.25.2.1.9</a>, LC_NUMERIC macro, <a href="#7.11">7.11</a>, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.11.2.1">7.11.2.1</a>
24619 <a href="#7.25.2.1.10">7.25.2.1.10</a>, <a href="#7.25.2.2.1">7.25.2.2.1</a> LC_TIME macro, <a href="#7.11">7.11</a>, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.23.3.5">7.23.3.5</a>
24620 <!--page 543 -->
24621 lconv structure type, <a href="#7.11">7.11</a> llabs function, <a href="#7.20.6.1">7.20.6.1</a>
24622 LDBL_DIG macro, <a href="#5.2.4.2.2">5.2.4.2.2</a> lldiv function, <a href="#7.20.6.2">7.20.6.2</a>
24624 LDBL_MANT_DIG macro, <a href="#5.2.4.2.2">5.2.4.2.2</a> LLONG_MAX macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#7.20.1.4">7.20.1.4</a>,
24626 LDBL_MAX_10_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a> LLONG_MIN macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#7.20.1.4">7.20.1.4</a>,
24628 LDBL_MIN macro, <a href="#5.2.4.2.2">5.2.4.2.2</a> llrint functions, <a href="#7.12.9.5">7.12.9.5</a>, <a href="#F.3">F.3</a>, <a href="#F.9.6.5">F.9.6.5</a>
24629 LDBL_MIN_10_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a> llrint type-generic macro, <a href="#7.22">7.22</a>
24630 LDBL_MIN_EXP macro, <a href="#5.2.4.2.2">5.2.4.2.2</a> llround functions, <a href="#7.12.9.7">7.12.9.7</a>, <a href="#F.9.6.7">F.9.6.7</a>
24631 ldexp functions, <a href="#7.12.6.6">7.12.6.6</a>, <a href="#F.9.3.6">F.9.3.6</a> llround type-generic macro, <a href="#7.22">7.22</a>
24634 ldiv_t type, <a href="#7.20">7.20</a> locale-specific behavior, <a href="#3.4.2">3.4.2</a>, <a href="#J.4">J.4</a>
24635 leading underscore in identifiers, <a href="#7.1.3">7.1.3</a> locale.h header, <a href="#7.11">7.11</a>, <a href="#7.26.5">7.26.5</a>
24636 left-shift assignment operator (<<=), <a href="#6.5.16.2">6.5.16.2</a> localeconv function, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.11.2.1">7.11.2.1</a>
24637 left-shift operator (<<), <a href="#6.5.7">6.5.7</a> localization, <a href="#7.11">7.11</a>
24639 external name, <a href="#5.2.4.1">5.2.4.1</a>, <a href="#6.4.2.1">6.4.2.1</a>, <a href="#6.11.3">6.11.3</a> log functions, <a href="#7.12.6.7">7.12.6.7</a>, <a href="#F.9.3.7">F.9.3.7</a>
24640 function name, <a href="#5.2.4.1">5.2.4.1</a>, <a href="#6.4.2.1">6.4.2.1</a>, <a href="#6.11.3">6.11.3</a> log type-generic macro, <a href="#7.22">7.22</a>
24641 identifier, <a href="#6.4.2.1">6.4.2.1</a> log10 functions, <a href="#7.12.6.8">7.12.6.8</a>, <a href="#F.9.3.8">F.9.3.8</a>
24642 internal name, <a href="#5.2.4.1">5.2.4.1</a>, <a href="#6.4.2.1">6.4.2.1</a> log10 type-generic macro, <a href="#7.22">7.22</a>
24643 length function, <a href="#7.20.7.1">7.20.7.1</a>, <a href="#7.21.6.3">7.21.6.3</a>, <a href="#7.24.4.6.1">7.24.4.6.1</a>, log1p functions, <a href="#7.12.6.9">7.12.6.9</a>, <a href="#F.9.3.9">F.9.3.9</a>
24645 length modifier, <a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.1">7.24.2.1</a>, log2 functions, <a href="#7.12.6.10">7.12.6.10</a>, <a href="#F.9.3.10">F.9.3.10</a>
24648 less-than-or-equal-to operator (<=), <a href="#6.5.8">6.5.8</a> complex, <a href="#7.3.7">7.3.7</a>, <a href="#G.6.3">G.6.3</a>
24649 letter, <a href="#5.2.1">5.2.1</a>, <a href="#7.4">7.4</a> real, <a href="#7.12.6">7.12.6</a>, <a href="#F.9.3">F.9.3</a>
24650 lexical elements, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#6.4">6.4</a> logb functions, <a href="#7.12.6.11">7.12.6.11</a>, <a href="#F.3">F.3</a>, <a href="#F.9.3.11">F.9.3.11</a>
24651 lgamma functions, <a href="#7.12.8.3">7.12.8.3</a>, <a href="#F.9.5.3">F.9.5.3</a> logb type-generic macro, <a href="#7.22">7.22</a>
24653 library, <a href="#5.1.1.1">5.1.1.1</a>, <a href="#7">7</a> AND (&&), <a href="#6.5.13">6.5.13</a>
24657 use of functions, <a href="#7.1.4">7.1.4</a> long double _Complex type, <a href="#6.2.5">6.2.5</a>
24659 limits <a href="#6.3.1.6">6.3.1.6</a>, <a href="#6.3.1.7">6.3.1.7</a>, <a href="#6.3.1.8">6.3.1.8</a>
24661 implementation, see implementation limits long double suffix, l or <a href="#L">L</a>, <a href="#6.4.4.2">6.4.4.2</a>
24662 numerical, see numerical limits long double type, <a href="#6.2.5">6.2.5</a>, <a href="#6.4.4.2">6.4.4.2</a>, <a href="#6.7.2">6.7.2</a>,
24663 translation, see translation limits <a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a>, <a href="#F.2">F.2</a>
24664 limits.h header, <a href="#4">4</a>, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#6.2.5">6.2.5</a>, <a href="#7.10">7.10</a> long double type conversion, <a href="#6.3.1.4">6.3.1.4</a>, <a href="#6.3.1.5">6.3.1.5</a>,
24665 line buffered stream, <a href="#7.19.3">7.19.3</a> <a href="#6.3.1.7">6.3.1.7</a>, <a href="#6.3.1.8">6.3.1.8</a>
24666 line number, <a href="#6.10.4">6.10.4</a>, <a href="#6.10.8">6.10.8</a> long int type, <a href="#6.2.5">6.2.5</a>, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.7.2">6.7.2</a>, <a href="#7.19.6.1">7.19.6.1</a>,
24667 line preprocessing directive, <a href="#6.10.4">6.10.4</a> <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a>
24668 lines, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#7.19.2">7.19.2</a> long int type conversion, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.3.1.3">6.3.1.3</a>,
24669 preprocessing directive, <a href="#6.10">6.10</a> <a href="#6.3.1.4">6.3.1.4</a>, <a href="#6.3.1.8">6.3.1.8</a>
24670 linkage, <a href="#6.2.2">6.2.2</a>, <a href="#6.7">6.7</a>, <a href="#6.7.4">6.7.4</a>, <a href="#6.7.5.2">6.7.5.2</a>, <a href="#6.9">6.9</a>, <a href="#6.9.2">6.9.2</a>, long integer suffix, l or <a href="#L">L</a>, <a href="#6.4.4.1">6.4.4.1</a>
24671 <a href="#6.11.2">6.11.2</a> long long int type, <a href="#6.2.5">6.2.5</a>, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.7.2">6.7.2</a>,
24672 <!--page 544 -->
24673 <a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a> mbsinit function, <a href="#7.24.6.2.1">7.24.6.2.1</a>
24674 long long int type conversion, <a href="#6.3.1.1">6.3.1.1</a>, mbsrtowcs function, <a href="#7.24.6.4.1">7.24.6.4.1</a>
24675 <a href="#6.3.1.3">6.3.1.3</a>, <a href="#6.3.1.4">6.3.1.4</a>, <a href="#6.3.1.8">6.3.1.8</a> mbstate_t type, <a href="#7.19.2">7.19.2</a>, <a href="#7.19.3">7.19.3</a>, <a href="#7.19.6.1">7.19.6.1</a>,
24676 long long integer suffix, ll or LL, <a href="#6.4.4.1">6.4.4.1</a> <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.1">7.24.1</a>, <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a>, <a href="#7.24.6">7.24.6</a>,
24677 LONG_MAX macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#7.20.1.4">7.20.1.4</a>, <a href="#7.24.4.1.2">7.24.4.1.2</a> <a href="#7.24.6.2.1">7.24.6.2.1</a>, <a href="#7.24.6.3">7.24.6.3</a>, <a href="#7.24.6.3.1">7.24.6.3.1</a>, <a href="#7.24.6.4">7.24.6.4</a>
24678 LONG_MIN macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#7.20.1.4">7.20.1.4</a>, <a href="#7.24.4.1.2">7.24.4.1.2</a> mbstowcs function, <a href="#6.4.5">6.4.5</a>, <a href="#7.20.8.1">7.20.8.1</a>, <a href="#7.24.6.4">7.24.6.4</a>
24679 longjmp function, <a href="#7.13.1.1">7.13.1.1</a>, <a href="#7.13.2.1">7.13.2.1</a>, <a href="#7.20.4.3">7.20.4.3</a> mbtowc function, <a href="#7.20.7.1">7.20.7.1</a>, <a href="#7.20.7.2">7.20.7.2</a>, <a href="#7.20.8.1">7.20.8.1</a>,
24681 low-order bit, <a href="#3.6">3.6</a> member access operators (. and ->), <a href="#6.5.2.3">6.5.2.3</a>
24683 lrint functions, <a href="#7.12.9.5">7.12.9.5</a>, <a href="#F.3">F.3</a>, <a href="#F.9.6.5">F.9.6.5</a> memchr function, <a href="#7.21.5.1">7.21.5.1</a>
24684 lrint type-generic macro, <a href="#7.22">7.22</a> memcmp function, <a href="#7.21.4">7.21.4</a>, <a href="#7.21.4.1">7.21.4.1</a>
24685 lround functions, <a href="#7.12.9.7">7.12.9.7</a>, <a href="#F.9.6.7">F.9.6.7</a> memcpy function, <a href="#7.21.2.1">7.21.2.1</a>
24686 lround type-generic macro, <a href="#7.22">7.22</a> memmove function, <a href="#7.21.2.2">7.21.2.2</a>
24687 lvalue, <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.1">6.5.1</a>, <a href="#6.5.2.4">6.5.2.4</a>, <a href="#6.5.3.1">6.5.3.1</a>, <a href="#6.5.16">6.5.16</a> memory management functions, <a href="#7.20.3">7.20.3</a>
24689 macro argument substitution, <a href="#6.10.3.1">6.10.3.1</a> minimum functions, <a href="#7.12.12">7.12.12</a>, <a href="#F.9.9">F.9.9</a>
24695 predefined, <a href="#6.10.8">6.10.8</a>, <a href="#6.11.9">6.11.9</a> modf functions, <a href="#7.12.6.12">7.12.6.12</a>, <a href="#F.9.3.12">F.9.3.12</a>
24698 macro parameter, <a href="#6.10.3">6.10.3</a> modulus, complex, <a href="#7.3.8.1">7.3.8.1</a>
24699 macro preprocessor, <a href="#6.10">6.10</a> multibyte character, <a href="#3.7.2">3.7.2</a>, <a href="#5.2.1.2">5.2.1.2</a>, <a href="#6.4.4.4">6.4.4.4</a>
24701 magnitude, complex, <a href="#7.3.8.1">7.3.8.1</a> wide character, <a href="#7.20.7">7.20.7</a>
24702 main function, <a href="#5.1.2.2.1">5.1.2.2.1</a>, <a href="#5.1.2.2.3">5.1.2.2.3</a>, <a href="#6.7.3.1">6.7.3.1</a>, <a href="#6.7.4">6.7.4</a>, extended, <a href="#7.24.6">7.24.6</a>
24704 malloc function, <a href="#7.20.3">7.20.3</a>, <a href="#7.20.3.2">7.20.3.2</a>, <a href="#7.20.3.3">7.20.3.3</a>, wide string, <a href="#7.20.8">7.20.8</a>
24709 matching failure, <a href="#7.24.2.6">7.24.2.6</a>, <a href="#7.24.2.8">7.24.2.8</a>, <a href="#7.24.2.10">7.24.2.10</a> extended, <a href="#7.24.6">7.24.6</a>
24710 math.h header, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.5">6.5</a>, <a href="#7.12">7.12</a>, <a href="#7.22">7.22</a>, <a href="#F">F</a>, <a href="#F.9">F.9</a>, restartable, <a href="#7.24.6.3">7.24.6.3</a>
24711 <a href="#J.5.17">J.5.17</a> multibyte/wide string conversion functions, <a href="#7.20.8">7.20.8</a>
24712 MATH_ERREXCEPT macro, <a href="#7.12">7.12</a>, <a href="#F.9">F.9</a> restartable, <a href="#7.24.6.4">7.24.6.4</a>
24713 math_errhandling macro, <a href="#7.1.3">7.1.3</a>, <a href="#7.12">7.12</a>, <a href="#F.9">F.9</a> multidimensional array, <a href="#6.5.2.1">6.5.2.1</a>
24714 MATH_ERRNO macro, <a href="#7.12">7.12</a> multiplication assignment operator (*=), <a href="#6.5.16.2">6.5.16.2</a>
24715 maximum functions, <a href="#7.12.12">7.12.12</a>, <a href="#F.9.9">F.9.9</a> multiplication operator (*), <a href="#6.5.5">6.5.5</a>, <a href="#F.3">F.3</a>, <a href="#G.5.1">G.5.1</a>
24716 MB_CUR_MAX macro, <a href="#7.1.1">7.1.1</a>, <a href="#7.20">7.20</a>, <a href="#7.20.7.2">7.20.7.2</a>, multiplicative expressions, <a href="#6.5.5">6.5.5</a>, <a href="#G.5.1">G.5.1</a>
24718 MB_LEN_MAX macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#7.1.1">7.1.1</a>, <a href="#7.20">7.20</a> n-char sequence, <a href="#7.20.1.3">7.20.1.3</a>
24719 mblen function, <a href="#7.20.7.1">7.20.7.1</a>, <a href="#7.24.6.3">7.24.6.3</a> n-wchar sequence, <a href="#7.24.4.1.1">7.24.4.1.1</a>
24721 mbrtowc function, <a href="#7.19.3">7.19.3</a>, <a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.19.6.2">7.19.6.2</a>, external, <a href="#5.2.4.1">5.2.4.1</a>, <a href="#6.4.2.1">6.4.2.1</a>, <a href="#6.11.3">6.11.3</a>
24722 <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a>, <a href="#7.24.6.3.1">7.24.6.3.1</a>, <a href="#7.24.6.3.2">7.24.6.3.2</a>, file, <a href="#7.19.3">7.19.3</a>
24723 <a href="#7.24.6.4.1">7.24.6.4.1</a> internal, <a href="#5.2.4.1">5.2.4.1</a>, <a href="#6.4.2.1">6.4.2.1</a>
24724 <!--page 545 -->
24730 nan functions, <a href="#7.12.11.2">7.12.11.2</a>, <a href="#F.2.1">F.2.1</a>, <a href="#F.9.8.2">F.9.8.2</a> operand, <a href="#6.4.6">6.4.6</a>, <a href="#6.5">6.5</a>
24731 NAN macro, <a href="#7.12">7.12</a>, <a href="#F.2.1">F.2.1</a> operating system, <a href="#5.1.2.1">5.1.2.1</a>, <a href="#7.20.4.6">7.20.4.6</a>
24733 nearbyint functions, <a href="#7.12.9.3">7.12.9.3</a>, <a href="#7.12.9.4">7.12.9.4</a>, <a href="#F.3">F.3</a>, operator, <a href="#6.4.6">6.4.6</a>
24735 nearbyint type-generic macro, <a href="#7.22">7.22</a> assignment, <a href="#6.5.16">6.5.16</a>
24736 nearest integer functions, <a href="#7.12.9">7.12.9</a>, <a href="#F.9.6">F.9.6</a> associativity, <a href="#6.5">6.5</a>
24738 negative zero, <a href="#6.2.6.2">6.2.6.2</a>, <a href="#7.12.11.1">7.12.11.1</a> multiplicative, <a href="#6.5.5">6.5.5</a>, <a href="#G.5.1">G.5.1</a>
24739 new-line character, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#5.2.1">5.2.1</a>, <a href="#6.4">6.4</a>, <a href="#6.10">6.10</a>, <a href="#6.10.4">6.10.4</a> postfix, <a href="#6.5.2">6.5.2</a>
24740 new-line escape sequence (\n), <a href="#5.2.2">5.2.2</a>, <a href="#6.4.4.4">6.4.4.4</a>, precedence, <a href="#6.5">6.5</a>
24741 <a href="#7.4.1.10">7.4.1.10</a> preprocessing, <a href="#6.10.1">6.10.1</a>, <a href="#6.10.3.2">6.10.3.2</a>, <a href="#6.10.3.3">6.10.3.3</a>, <a href="#6.10.9">6.10.9</a>
24742 nextafter functions, <a href="#7.12.11.3">7.12.11.3</a>, <a href="#7.12.11.4">7.12.11.4</a>, <a href="#F.3">F.3</a>, relational, <a href="#6.5.8">6.5.8</a>
24745 nexttoward functions, <a href="#7.12.11.4">7.12.11.4</a>, <a href="#F.3">F.3</a>, <a href="#F.9.8.4">F.9.8.4</a> unary arithmetic, <a href="#6.5.3.3">6.5.3.3</a>
24748 non-stop floating-point control mode, <a href="#7.6.4.2">7.6.4.2</a> bitwise exclusive (^), <a href="#6.5.11">6.5.11</a>
24749 nongraphic characters, <a href="#5.2.2">5.2.2</a>, <a href="#6.4.4.4">6.4.4.4</a> bitwise exclusive assignment (^=), <a href="#6.5.16.2">6.5.16.2</a>
24750 nonlocal jumps header, <a href="#7.13">7.13</a> bitwise inclusive (|), <a href="#6.5.12">6.5.12</a>
24751 norm, complex, <a href="#7.3.8.1">7.3.8.1</a> bitwise inclusive assignment (|=), <a href="#6.5.16.2">6.5.16.2</a>
24755 null character (\0), <a href="#5.2.1">5.2.1</a>, <a href="#6.4.4.4">6.4.4.4</a>, <a href="#6.4.5">6.4.5</a> order of evaluation, <a href="#6.5">6.5</a>
24756 padding of binary stream, <a href="#7.19.2">7.19.2</a> ordinary identifier name space, <a href="#6.2.3">6.2.3</a>
24757 NULL macro, <a href="#7.11">7.11</a>, <a href="#7.17">7.17</a>, <a href="#7.19.1">7.19.1</a>, <a href="#7.20">7.20</a>, <a href="#7.21.1">7.21.1</a>, orientation of stream, <a href="#7.19.2">7.19.2</a>, <a href="#7.24.3.5">7.24.3.5</a>
24758 <a href="#7.23.1">7.23.1</a>, <a href="#7.24.1">7.24.1</a> outer scope, <a href="#6.2.1">6.2.1</a>
24761 null preprocessing directive, <a href="#6.10.7">6.10.7</a> binary stream, <a href="#7.19.2">7.19.2</a>
24762 null statement, <a href="#6.8.3">6.8.3</a> bits, <a href="#6.2.6.2">6.2.6.2</a>, <a href="#7.18.1.1">7.18.1.1</a>
24763 null wide character, <a href="#7.1.1">7.1.1</a> structure/union, <a href="#6.2.6.1">6.2.6.1</a>, <a href="#6.7.2.1">6.7.2.1</a>
24764 number classification macros, <a href="#7.12">7.12</a>, <a href="#7.12.3.1">7.12.3.1</a> parameter, <a href="#3.15">3.15</a>
24765 numeric conversion functions, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.20.1">7.20.1</a> array, <a href="#6.9.1">6.9.1</a>
24766 wide string, <a href="#7.8.2.4">7.8.2.4</a>, <a href="#7.24.4.1">7.24.4.1</a> ellipsis, <a href="#6.7.5.3">6.7.5.3</a>, <a href="#6.10.3">6.10.3</a>
24767 numerical limits, <a href="#5.2.4.2">5.2.4.2</a> function, <a href="#6.5.2.2">6.5.2.2</a>, <a href="#6.7">6.7</a>, <a href="#6.9.1">6.9.1</a>
24770 object representation, <a href="#6.2.6.1">6.2.6.1</a> program, <a href="#5.1.2.2.1">5.1.2.2.1</a>
24772 object-like macro, <a href="#6.10.3">6.10.3</a> parentheses punctuator (( )), <a href="#6.7.5.3">6.7.5.3</a>, <a href="#6.8.4">6.8.4</a>, <a href="#6.8.5">6.8.5</a>
24773 obsolescence, <a href="#6.11">6.11</a>, <a href="#7.26">7.26</a> parenthesized expression, <a href="#6.5.1">6.5.1</a>
24775 octal digit, <a href="#6.4.4.1">6.4.4.1</a>, <a href="#6.4.4.4">6.4.4.4</a> permitted form of initializer, <a href="#6.6">6.6</a>
24776 <!--page 546 -->
24777 perror function, <a href="#7.19.10.4">7.19.10.4</a> PRIcPTR macros, <a href="#7.8.1">7.8.1</a>
24778 phase angle, complex, <a href="#7.3.9.1">7.3.9.1</a> primary expression, <a href="#6.5.1">6.5.1</a>
24779 physical source lines, <a href="#5.1.1.2">5.1.1.2</a> printf function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.6.3">7.19.6.3</a>, <a href="#7.19.6.10">7.19.6.10</a>
24780 placemarker, <a href="#6.10.3.3">6.10.3.3</a> printing character, <a href="#5.2.2">5.2.2</a>, <a href="#7.4">7.4</a>, <a href="#7.4.1.8">7.4.1.8</a>
24781 plus operator, unary, <a href="#6.5.3.3">6.5.3.3</a> printing wide character, <a href="#7.25.2">7.25.2</a>
24782 pointer arithmetic, <a href="#6.5.6">6.5.6</a> program diagnostics, <a href="#7.2.1">7.2.1</a>
24783 pointer comparison, <a href="#6.5.8">6.5.8</a> program execution, <a href="#5.1.2.2.2">5.1.2.2.2</a>, <a href="#5.1.2.3">5.1.2.3</a>
24784 pointer declarator, <a href="#6.7.5.1">6.7.5.1</a> program file, <a href="#5.1.1.1">5.1.1.1</a>
24785 pointer operator (->), <a href="#6.5.2.3">6.5.2.3</a> program image, <a href="#5.1.1.2">5.1.1.2</a>
24786 pointer to function, <a href="#6.5.2.2">6.5.2.2</a> program name (argv[0]), <a href="#5.1.2.2.1">5.1.2.2.1</a>
24787 pointer type, <a href="#6.2.5">6.2.5</a> program parameters, <a href="#5.1.2.2.1">5.1.2.2.1</a>
24788 pointer type conversion, <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.3.2.3">6.3.2.3</a> program startup, <a href="#5.1.2">5.1.2</a>, <a href="#5.1.2.1">5.1.2.1</a>, <a href="#5.1.2.2.1">5.1.2.2.1</a>
24789 pointer, null, <a href="#6.3.2.3">6.3.2.3</a> program structure, <a href="#5.1.1.1">5.1.1.1</a>
24790 portability, <a href="#4">4</a>, <a href="#J">J</a> program termination, <a href="#5.1.2">5.1.2</a>, <a href="#5.1.2.1">5.1.2.1</a>, <a href="#5.1.2.2.3">5.1.2.2.3</a>,
24792 positive difference, <a href="#7.12.12.1">7.12.12.1</a> program, conforming, <a href="#4">4</a>
24793 positive difference functions, <a href="#7.12.12">7.12.12</a>, <a href="#F.9.9">F.9.9</a> program, strictly conforming, <a href="#4">4</a>
24794 postfix decrement operator (--), <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.2.4">6.5.2.4</a> promotions
24795 postfix expressions, <a href="#6.5.2">6.5.2</a> default argument, <a href="#6.5.2.2">6.5.2.2</a>
24796 postfix increment operator (++), <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.2.4">6.5.2.4</a> integer, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#6.3.1.1">6.3.1.1</a>
24797 pow functions, <a href="#7.12.7.4">7.12.7.4</a>, <a href="#F.9.4.4">F.9.4.4</a> prototype, see function prototype
24798 pow type-generic macro, <a href="#7.22">7.22</a> pseudo-random sequence functions, <a href="#7.20.2">7.20.2</a>
24800 complex, <a href="#7.3.8">7.3.8</a>, <a href="#G.6.4">G.6.4</a> PTRDIFF_MIN macro, <a href="#7.18.3">7.18.3</a>
24801 real, <a href="#7.12.7">7.12.7</a>, <a href="#F.9.4">F.9.4</a> ptrdiff_t type, <a href="#7.17">7.17</a>, <a href="#7.18.3">7.18.3</a>, <a href="#7.19.6.1">7.19.6.1</a>,
24802 pp-number, <a href="#6.4.8">6.4.8</a> <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a>
24804 pragma preprocessing directive, <a href="#6.10.6">6.10.6</a>, <a href="#6.11.8">6.11.8</a> putc function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.7.8">7.19.7.8</a>, <a href="#7.19.7.9">7.19.7.9</a>
24805 precedence of operators, <a href="#6.5">6.5</a> putchar function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.7.9">7.19.7.9</a>
24806 precedence of syntax rules, <a href="#5.1.1.2">5.1.1.2</a> puts function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.7.10">7.19.7.10</a>
24807 precision, <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.24.2.1">7.24.2.1</a> putwc function, <a href="#7.19.1">7.19.1</a>, <a href="#7.24.3.8">7.24.3.8</a>, <a href="#7.24.3.9">7.24.3.9</a>
24808 excess, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.3.1.5">6.3.1.5</a>, <a href="#6.3.1.8">6.3.1.8</a>, <a href="#6.8.6.4">6.8.6.4</a> putwchar function, <a href="#7.19.1">7.19.1</a>, <a href="#7.24.3.9">7.24.3.9</a>
24810 prefix decrement operator (--), <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.3.1">6.5.3.1</a> qsort function, <a href="#7.20.5">7.20.5</a>, <a href="#7.20.5.2">7.20.5.2</a>
24811 prefix increment operator (++), <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.3.1">6.5.3.1</a> qualified types, <a href="#6.2.5">6.2.5</a>
24812 preprocessing concatenation, <a href="#6.10.3.3">6.10.3.3</a> qualified version of type, <a href="#6.2.5">6.2.5</a>
24813 preprocessing directives, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#6.10">6.10</a> question-mark escape sequence (\?), <a href="#6.4.4.4">6.4.4.4</a>
24814 preprocessing file, <a href="#5.1.1.1">5.1.1.1</a>, <a href="#6.10">6.10</a> quiet NaN, <a href="#5.2.4.2.2">5.2.4.2.2</a>
24816 preprocessing operators raise function, <a href="#7.14">7.14</a>, <a href="#7.14.1.1">7.14.1.1</a>, <a href="#7.14.2.1">7.14.2.1</a>, <a href="#7.20.4.1">7.20.4.1</a>
24817 #, <a href="#6.10.3.2">6.10.3.2</a> rand function, <a href="#7.20">7.20</a>, <a href="#7.20.2.1">7.20.2.1</a>, <a href="#7.20.2.2">7.20.2.2</a>
24818 ##, <a href="#6.10.3.3">6.10.3.3</a> RAND_MAX macro, <a href="#7.20">7.20</a>, <a href="#7.20.2.1">7.20.2.1</a>
24820 defined, <a href="#6.10.1">6.10.1</a> excess, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.3.1.5">6.3.1.5</a>, <a href="#6.3.1.8">6.3.1.8</a>, <a href="#6.8.6.4">6.8.6.4</a>
24821 preprocessing tokens, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#6.4">6.4</a>, <a href="#6.10">6.10</a> range error, <a href="#7.12.1">7.12.1</a>, <a href="#7.12.5.3">7.12.5.3</a>, <a href="#7.12.5.4">7.12.5.4</a>, <a href="#7.12.5.5">7.12.5.5</a>,
24822 preprocessing translation unit, <a href="#5.1.1.1">5.1.1.1</a> <a href="#7.12.6.1">7.12.6.1</a>, <a href="#7.12.6.2">7.12.6.2</a>, <a href="#7.12.6.3">7.12.6.3</a>, <a href="#7.12.6.5">7.12.6.5</a>,
24823 preprocessor, <a href="#6.10">6.10</a> <a href="#7.12.6.6">7.12.6.6</a>, <a href="#7.12.6.7">7.12.6.7</a>, <a href="#7.12.6.8">7.12.6.8</a>, <a href="#7.12.6.9">7.12.6.9</a>,
24824 PRIcFASTN macros, <a href="#7.8.1">7.8.1</a> <a href="#7.12.6.10">7.12.6.10</a>, <a href="#7.12.6.11">7.12.6.11</a>, <a href="#7.12.6.13">7.12.6.13</a>, <a href="#7.12.7.3">7.12.7.3</a>,
24825 PRIcLEASTN macros, <a href="#7.8.1">7.8.1</a> <a href="#7.12.7.4">7.12.7.4</a>, <a href="#7.12.8.2">7.12.8.2</a>, <a href="#7.12.8.3">7.12.8.3</a>, <a href="#7.12.8.4">7.12.8.4</a>,
24826 PRIcMAX macros, <a href="#7.8.1">7.8.1</a> <a href="#7.12.9.5">7.12.9.5</a>, <a href="#7.12.9.7">7.12.9.7</a>, <a href="#7.12.11.3">7.12.11.3</a>, <a href="#7.12.12.1">7.12.12.1</a>,
24828 <!--page 547 -->
24830 real floating type conversion, <a href="#6.3.1.4">6.3.1.4</a>, <a href="#6.3.1.5">6.3.1.5</a>, save calling environment function, <a href="#7.13.1">7.13.1</a>
24831 <a href="#6.3.1.7">6.3.1.7</a>, <a href="#F.3">F.3</a>, <a href="#F.4">F.4</a> scalar types, <a href="#6.2.5">6.2.5</a>
24832 real floating types, <a href="#6.2.5">6.2.5</a> scalbln function, <a href="#7.12.6.13">7.12.6.13</a>, <a href="#F.3">F.3</a>, <a href="#F.9.3.13">F.9.3.13</a>
24833 real type domain, <a href="#6.2.5">6.2.5</a> scalbln type-generic macro, <a href="#7.22">7.22</a>
24834 real types, <a href="#6.2.5">6.2.5</a> scalbn function, <a href="#7.12.6.13">7.12.6.13</a>, <a href="#F.3">F.3</a>, <a href="#F.9.3.13">F.9.3.13</a>
24835 real-floating, <a href="#7.12.3">7.12.3</a> scalbn type-generic macro, <a href="#7.22">7.22</a>
24836 realloc function, <a href="#7.20.3">7.20.3</a>, <a href="#7.20.3.2">7.20.3.2</a>, <a href="#7.20.3.4">7.20.3.4</a> scanf function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.6.4">7.19.6.4</a>, <a href="#7.19.6.11">7.19.6.11</a>
24837 recommended practice, <a href="#3.16">3.16</a> scanlist, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.2">7.24.2.2</a>
24838 recursion, <a href="#6.5.2.2">6.5.2.2</a> scanset, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.2">7.24.2.2</a>
24839 recursive function call, <a href="#6.5.2.2">6.5.2.2</a> SCHAR_MAX macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>
24840 redefinition of macro, <a href="#6.10.3">6.10.3</a> SCHAR_MIN macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>
24841 reentrancy, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#5.2.3">5.2.3</a> SCNcFASTN macros, <a href="#7.8.1">7.8.1</a>
24844 register storage-class specifier, <a href="#6.7.1">6.7.1</a>, <a href="#6.9">6.9</a> SCNcN macros, <a href="#7.8.1">7.8.1</a>
24846 reliability of data, interrupted, <a href="#5.1.2.3">5.1.2.3</a> scope of identifier, <a href="#6.2.1">6.2.1</a>, <a href="#6.9.2">6.9.2</a>
24848 remainder functions, <a href="#7.12.10">7.12.10</a>, <a href="#F.9.7">F.9.7</a> string, <a href="#7.21.5">7.21.5</a>
24849 remainder functions, <a href="#7.12.10.2">7.12.10.2</a>, <a href="#7.12.10.3">7.12.10.3</a>, <a href="#F.3">F.3</a>, utility, <a href="#7.20.5">7.20.5</a>
24851 remainder operator (%), <a href="#6.5.5">6.5.5</a> SEEK_CUR macro, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.9.2">7.19.9.2</a>
24852 remainder type-generic macro, <a href="#7.22">7.22</a> SEEK_END macro, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.9.2">7.19.9.2</a>
24853 remove function, <a href="#7.19.4.1">7.19.4.1</a>, <a href="#7.19.4.4">7.19.4.4</a> SEEK_SET macro, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.9.2">7.19.9.2</a>
24854 remquo functions, <a href="#7.12.10.3">7.12.10.3</a>, <a href="#F.3">F.3</a>, <a href="#F.9.7.3">F.9.7.3</a> selection statements, <a href="#6.8.4">6.8.4</a>
24855 remquo type-generic macro, <a href="#7.22">7.22</a> self-referential structure, <a href="#6.7.2.3">6.7.2.3</a>
24856 rename function, <a href="#7.19.4.2">7.19.4.2</a> semicolon punctuator (;), <a href="#6.7">6.7</a>, <a href="#6.7.2.1">6.7.2.1</a>, <a href="#6.8.3">6.8.3</a>,
24857 representations of types, <a href="#6.2.6">6.2.6</a> <a href="#6.8.5">6.8.5</a>, <a href="#6.8.6">6.8.6</a>
24859 rescanning and replacement, <a href="#6.10.3.4">6.10.3.4</a> separate translation, <a href="#5.1.1.1">5.1.1.1</a>
24860 reserved identifiers, <a href="#6.4.1">6.4.1</a>, <a href="#7.1.3">7.1.3</a> sequence points, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#6.5">6.5</a>, <a href="#6.8">6.8</a>, <a href="#7.1.4">7.1.4</a>, <a href="#7.19.6">7.19.6</a>,
24861 restartable multibyte/wide character conversion <a href="#7.20.5">7.20.5</a>, <a href="#7.24.2">7.24.2</a>, <a href="#C">C</a>
24863 restartable multibyte/wide string conversion setbuf function, <a href="#7.19.3">7.19.3</a>, <a href="#7.19.5.1">7.19.5.1</a>, <a href="#7.19.5.5">7.19.5.5</a>
24864 functions, <a href="#7.24.6.4">7.24.6.4</a> setjmp macro, <a href="#7.1.3">7.1.3</a>, <a href="#7.13.1.1">7.13.1.1</a>, <a href="#7.13.2.1">7.13.2.1</a>
24865 restore calling environment function, <a href="#7.13.2">7.13.2</a> setjmp.h header, <a href="#7.13">7.13</a>
24866 restrict type qualifier, <a href="#6.7.3">6.7.3</a>, <a href="#6.7.3.1">6.7.3.1</a> setlocale function, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.11.2.1">7.11.2.1</a>
24867 restrict-qualified type, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.3">6.7.3</a> setvbuf function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.3">7.19.3</a>, <a href="#7.19.5.1">7.19.5.1</a>,
24868 return statement, <a href="#6.8.6.4">6.8.6.4</a> <a href="#7.19.5.5">7.19.5.5</a>, <a href="#7.19.5.6">7.19.5.6</a>
24869 rewind function, <a href="#7.19.5.3">7.19.5.3</a>, <a href="#7.19.7.11">7.19.7.11</a>, <a href="#7.19.9.5">7.19.9.5</a>, shall, <a href="#4">4</a>
24871 right-shift assignment operator (>>=), <a href="#6.5.16.2">6.5.16.2</a> shift sequence, <a href="#7.1.1">7.1.1</a>
24872 right-shift operator (>>), <a href="#6.5.7">6.5.7</a> shift states, <a href="#5.2.1.2">5.2.1.2</a>
24873 rint functions, <a href="#7.12.9.4">7.12.9.4</a>, <a href="#F.3">F.3</a>, <a href="#F.9.6.4">F.9.6.4</a> short identifier, character, <a href="#5.2.4.1">5.2.4.1</a>, <a href="#6.4.3">6.4.3</a>
24874 rint type-generic macro, <a href="#7.22">7.22</a> short int type, <a href="#6.2.5">6.2.5</a>, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.7.2">6.7.2</a>, <a href="#7.19.6.1">7.19.6.1</a>,
24875 round functions, <a href="#7.12.9.6">7.12.9.6</a>, <a href="#F.9.6.6">F.9.6.6</a> <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a>
24876 round type-generic macro, <a href="#7.22">7.22</a> short int type conversion, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.3.1.3">6.3.1.3</a>,
24877 rounding mode, floating point, <a href="#5.2.4.2.2">5.2.4.2.2</a> <a href="#6.3.1.4">6.3.1.4</a>, <a href="#6.3.1.8">6.3.1.8</a>
24880 <!--page 548 -->
24881 side effects, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#6.5">6.5</a> source lines, <a href="#5.1.1.2">5.1.1.2</a>
24882 SIG_ATOMIC_MAX macro, <a href="#7.18.3">7.18.3</a> source text, <a href="#5.1.1.2">5.1.1.2</a>
24883 SIG_ATOMIC_MIN macro, <a href="#7.18.3">7.18.3</a> space character (' '), <a href="#5.1.1.2">5.1.1.2</a>, <a href="#5.2.1">5.2.1</a>, <a href="#6.4">6.4</a>, <a href="#7.4.1.3">7.4.1.3</a>,
24884 sig_atomic_t type, <a href="#7.14">7.14</a>, <a href="#7.14.1.1">7.14.1.1</a>, <a href="#7.18.3">7.18.3</a> <a href="#7.4.1.10">7.4.1.10</a>, <a href="#7.25.2.1.3">7.25.2.1.3</a>
24885 SIG_DFL macro, <a href="#7.14">7.14</a>, <a href="#7.14.1.1">7.14.1.1</a> sprintf function, <a href="#7.19.6.6">7.19.6.6</a>, <a href="#7.19.6.13">7.19.6.13</a>
24886 SIG_ERR macro, <a href="#7.14">7.14</a>, <a href="#7.14.1.1">7.14.1.1</a> sqrt functions, <a href="#7.12.7.5">7.12.7.5</a>, <a href="#F.3">F.3</a>, <a href="#F.9.4.5">F.9.4.5</a>
24887 SIG_IGN macro, <a href="#7.14">7.14</a>, <a href="#7.14.1.1">7.14.1.1</a> sqrt type-generic macro, <a href="#7.22">7.22</a>
24888 SIGABRT macro, <a href="#7.14">7.14</a>, <a href="#7.20.4.1">7.20.4.1</a> srand function, <a href="#7.20.2.2">7.20.2.2</a>
24889 SIGFPE macro, <a href="#7.14">7.14</a>, <a href="#7.14.1.1">7.14.1.1</a>, <a href="#J.5.17">J.5.17</a> sscanf function, <a href="#7.19.6.7">7.19.6.7</a>, <a href="#7.19.6.14">7.19.6.14</a>
24890 SIGILL macro, <a href="#7.14">7.14</a>, <a href="#7.14.1.1">7.14.1.1</a> standard error stream, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.3">7.19.3</a>, <a href="#7.19.10.4">7.19.10.4</a>
24891 SIGINT macro, <a href="#7.14">7.14</a> standard headers, <a href="#4">4</a>, <a href="#7.1.2">7.1.2</a>
24892 sign and magnitude, <a href="#6.2.6.2">6.2.6.2</a> <a href="#7.2"><assert.h></a>, <a href="#7.2">7.2</a>, <a href="#B.1">B.1</a>
24893 sign bit, <a href="#6.2.6.2">6.2.6.2</a> <a href="#7.3"><complex.h></a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.3">7.3</a>, <a href="#7.22">7.22</a>, <a href="#7.26.1">7.26.1</a>,
24894 signal function, <a href="#7.14.1.1">7.14.1.1</a>, <a href="#7.20.4.4">7.20.4.4</a> <a href="#G.6">G.6</a>, <a href="#J.5.17">J.5.17</a>
24895 signal handler, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#5.2.3">5.2.3</a>, <a href="#7.14.1.1">7.14.1.1</a>, <a href="#7.14.2.1">7.14.2.1</a> <a href="#7.4"><ctype.h></a>, <a href="#7.4">7.4</a>, <a href="#7.26.2">7.26.2</a>
24896 signal handling functions, <a href="#7.14.1">7.14.1</a> <a href="#7.5"><errno.h></a>, <a href="#7.5">7.5</a>, <a href="#7.26.3">7.26.3</a>
24897 signal.h header, <a href="#7.14">7.14</a>, <a href="#7.26.6">7.26.6</a> <a href="#7.6"><fenv.h></a>, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.6">7.6</a>, <a href="#7.12">7.12</a>, <a href="#F">F</a>, <a href="#H">H</a>
24898 signaling NaN, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#F.2.1">F.2.1</a> <a href="#7.7"><float.h></a>, <a href="#4">4</a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.7">7.7</a>, <a href="#7.20.1.3">7.20.1.3</a>,
24899 signals, <a href="#5.1.2.3">5.1.2.3</a>, <a href="#5.2.3">5.2.3</a>, <a href="#7.14.1">7.14.1</a> <a href="#7.24.4.1.1">7.24.4.1.1</a>
24900 signbit macro, <a href="#7.12.3.6">7.12.3.6</a>, <a href="#F.3">F.3</a> <a href="#7.8"><inttypes.h></a>, <a href="#7.8">7.8</a>, <a href="#7.26.4">7.26.4</a>
24901 signed char type, <a href="#6.2.5">6.2.5</a>, <a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.9"><iso646.h></a>, <a href="#4">4</a>, <a href="#7.9">7.9</a>
24902 <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a> <a href="#7.10"><limits.h></a>, <a href="#4">4</a>, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#6.2.5">6.2.5</a>, <a href="#7.10">7.10</a>
24903 signed character, <a href="#6.3.1.1">6.3.1.1</a> <a href="#7.11"><locale.h></a>, <a href="#7.11">7.11</a>, <a href="#7.26.5">7.26.5</a>
24904 signed integer types, <a href="#6.2.5">6.2.5</a>, <a href="#6.3.1.3">6.3.1.3</a>, <a href="#6.4.4.1">6.4.4.1</a> <a href="#7.12"><math.h></a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#6.5">6.5</a>, <a href="#7.12">7.12</a>, <a href="#7.22">7.22</a>, <a href="#F">F</a>, <a href="#F.9">F.9</a>,
24905 signed type conversion, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.3.1.3">6.3.1.3</a>, <a href="#6.3.1.4">6.3.1.4</a>, <a href="#J.5.17">J.5.17</a>
24907 signed types, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.2">6.7.2</a> <a href="#7.14"><signal.h></a>, <a href="#7.14">7.14</a>, <a href="#7.26.6">7.26.6</a>
24908 significand part, <a href="#6.4.4.2">6.4.4.2</a> <a href="#7.15"><stdarg.h></a>, <a href="#4">4</a>, <a href="#6.7.5.3">6.7.5.3</a>, <a href="#7.15">7.15</a>
24909 SIGSEGV macro, <a href="#7.14">7.14</a>, <a href="#7.14.1.1">7.14.1.1</a> <a href="#7.16"><stdbool.h></a>, <a href="#4">4</a>, <a href="#7.16">7.16</a>, <a href="#7.26.7">7.26.7</a>, <a href="#H">H</a>
24910 SIGTERM macro, <a href="#7.14">7.14</a> <a href="#7.17"><stddef.h></a>, <a href="#4">4</a>, <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.3.2.3">6.3.2.3</a>, <a href="#6.4.4.4">6.4.4.4</a>,
24911 simple assignment operator (=), <a href="#6.5.16.1">6.5.16.1</a> <a href="#6.4.5">6.4.5</a>, <a href="#6.5.3.4">6.5.3.4</a>, <a href="#6.5.6">6.5.6</a>, <a href="#7.17">7.17</a>
24912 sin functions, <a href="#7.12.4.6">7.12.4.6</a>, <a href="#F.9.1.6">F.9.1.6</a> <a href="#7.18"><stdint.h></a>, <a href="#4">4</a>, <a href="#5.2.4.2">5.2.4.2</a>, <a href="#6.10.1">6.10.1</a>, <a href="#7.8">7.8</a>, <a href="#7.18">7.18</a>,
24913 sin type-generic macro, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</a> <a href="#7.26.8">7.26.8</a>
24914 single-byte character, <a href="#3.7.1">3.7.1</a>, <a href="#5.2.1.2">5.2.1.2</a> <a href="#7.19"><stdio.h></a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.19">7.19</a>, <a href="#7.26.9">7.26.9</a>, <a href="#F">F</a>
24915 single-byte/wide character conversion functions, <a href="#7.20"><stdlib.h></a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.20">7.20</a>, <a href="#7.26.10">7.26.10</a>, <a href="#F">F</a>
24916 <a href="#7.24.6.1">7.24.6.1</a> <a href="#7.21"><string.h></a>, <a href="#7.21">7.21</a>, <a href="#7.26.11">7.26.11</a>
24917 single-precision arithmetic, <a href="#5.1.2.3">5.1.2.3</a> <a href="#7.22"><tgmath.h></a>, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</a>
24918 single-quote escape sequence (\'), <a href="#6.4.4.4">6.4.4.4</a>, <a href="#6.4.5">6.4.5</a> <a href="#7.23"><time.h></a>, <a href="#7.23">7.23</a>
24919 sinh functions, <a href="#7.12.5.5">7.12.5.5</a>, <a href="#F.9.2.5">F.9.2.5</a> <a href="#7.24"><wchar.h></a>, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.19.1">7.19.1</a>, <a href="#7.24">7.24</a>, <a href="#7.26.12">7.26.12</a>,
24921 SIZE_MAX macro, <a href="#7.18.3">7.18.3</a> <a href="#7.25"><wctype.h></a>, <a href="#7.25">7.25</a>, <a href="#7.26.13">7.26.13</a>
24922 size_t type, <a href="#6.5.3.4">6.5.3.4</a>, <a href="#7.17">7.17</a>, <a href="#7.18.3">7.18.3</a>, <a href="#7.19.1">7.19.1</a>, standard input stream, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.3">7.19.3</a>
24923 <a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.20">7.20</a>, <a href="#7.21.1">7.21.1</a>, <a href="#7.23.1">7.23.1</a>, standard integer types, <a href="#6.2.5">6.2.5</a>
24924 <a href="#7.24.1">7.24.1</a>, <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a> standard output stream, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.3">7.19.3</a>
24925 sizeof operator, <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.3">6.5.3</a>, <a href="#6.5.3.4">6.5.3.4</a> standard signed integer types, <a href="#6.2.5">6.2.5</a>
24926 snprintf function, <a href="#7.19.6.5">7.19.6.5</a>, <a href="#7.19.6.12">7.19.6.12</a> state-dependent encoding, <a href="#5.2.1.2">5.2.1.2</a>, <a href="#7.20.7">7.20.7</a>
24928 source character set, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#5.2.1">5.2.1</a> break, <a href="#6.8.6.3">6.8.6.3</a>
24930 name, <a href="#6.10.4">6.10.4</a>, <a href="#6.10.8">6.10.8</a> continue, <a href="#6.8.6.2">6.8.6.2</a>
24932 <!--page 549 -->
24940 labeled, <a href="#6.8.1">6.8.1</a> literal, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#5.2.1">5.2.1</a>, <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.4.5">6.4.5</a>, <a href="#6.5.1">6.5.1</a>, <a href="#6.7.8">6.7.8</a>
24942 return, <a href="#6.8.6.4">6.8.6.4</a> numeric conversion functions, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.20.1">7.20.1</a>
24945 switch, <a href="#6.8.4.2">6.8.4.2</a> string.h header, <a href="#7.21">7.21</a>, <a href="#7.26.11">7.26.11</a>
24946 while, <a href="#6.8.5.1">6.8.5.1</a> stringizing, <a href="#6.10.3.2">6.10.3.2</a>, <a href="#6.10.9">6.10.9</a>
24947 static storage duration, <a href="#6.2.4">6.2.4</a> strlen function, <a href="#7.21.6.3">7.21.6.3</a>
24948 static storage-class specifier, <a href="#6.2.2">6.2.2</a>, <a href="#6.2.4">6.2.4</a>, <a href="#6.7.1">6.7.1</a> strncat function, <a href="#7.21.3.2">7.21.3.2</a>
24949 static, in array declarators, <a href="#6.7.5.2">6.7.5.2</a>, <a href="#6.7.5.3">6.7.5.3</a> strncmp function, <a href="#7.21.4">7.21.4</a>, <a href="#7.21.4.4">7.21.4.4</a>
24950 stdarg.h header, <a href="#4">4</a>, <a href="#6.7.5.3">6.7.5.3</a>, <a href="#7.15">7.15</a> strncpy function, <a href="#7.21.2.4">7.21.2.4</a>
24951 stdbool.h header, <a href="#4">4</a>, <a href="#7.16">7.16</a>, <a href="#7.26.7">7.26.7</a>, <a href="#H">H</a> strpbrk function, <a href="#7.21.5.4">7.21.5.4</a>
24952 STDC, <a href="#6.10.6">6.10.6</a>, <a href="#6.11.8">6.11.8</a> strrchr function, <a href="#7.21.5.5">7.21.5.5</a>
24953 stddef.h header, <a href="#4">4</a>, <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.3.2.3">6.3.2.3</a>, <a href="#6.4.4.4">6.4.4.4</a>, strspn function, <a href="#7.21.5.6">7.21.5.6</a>
24954 <a href="#6.4.5">6.4.5</a>, <a href="#6.5.3.4">6.5.3.4</a>, <a href="#6.5.6">6.5.6</a>, <a href="#7.17">7.17</a> strstr function, <a href="#7.21.5.7">7.21.5.7</a>
24955 stderr macro, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.2">7.19.2</a>, <a href="#7.19.3">7.19.3</a> strtod function, <a href="#7.12.11.2">7.12.11.2</a>, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.20.1.3">7.20.1.3</a>,
24956 stdin macro, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.2">7.19.2</a>, <a href="#7.19.3">7.19.3</a>, <a href="#7.19.6.4">7.19.6.4</a>, <a href="#7.24.2.2">7.24.2.2</a>, <a href="#F.3">F.3</a>
24957 <a href="#7.19.7.6">7.19.7.6</a>, <a href="#7.19.7.7">7.19.7.7</a>, <a href="#7.24.2.12">7.24.2.12</a>, <a href="#7.24.3.7">7.24.3.7</a> strtof function, <a href="#7.12.11.2">7.12.11.2</a>, <a href="#7.20.1.3">7.20.1.3</a>, <a href="#F.3">F.3</a>
24958 stdint.h header, <a href="#4">4</a>, <a href="#5.2.4.2">5.2.4.2</a>, <a href="#6.10.1">6.10.1</a>, <a href="#7.8">7.8</a>, <a href="#7.18">7.18</a>, strtoimax function, <a href="#7.8.2.3">7.8.2.3</a>
24960 stdio.h header, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.19">7.19</a>, <a href="#7.26.9">7.26.9</a>, <a href="#F">F</a> strtol function, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.20.1.2">7.20.1.2</a>,
24961 stdlib.h header, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.20">7.20</a>, <a href="#7.26.10">7.26.10</a>, <a href="#F">F</a> <a href="#7.20.1.4">7.20.1.4</a>, <a href="#7.24.2.2">7.24.2.2</a>
24962 stdout macro, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.2">7.19.2</a>, <a href="#7.19.3">7.19.3</a>, <a href="#7.19.6.3">7.19.6.3</a>, strtold function, <a href="#7.12.11.2">7.12.11.2</a>, <a href="#7.20.1.3">7.20.1.3</a>, <a href="#F.3">F.3</a>
24963 <a href="#7.19.7.9">7.19.7.9</a>, <a href="#7.19.7.10">7.19.7.10</a>, <a href="#7.24.2.11">7.24.2.11</a>, <a href="#7.24.3.9">7.24.3.9</a> strtoll function, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.20.1.2">7.20.1.2</a>, <a href="#7.20.1.4">7.20.1.4</a>
24964 storage duration, <a href="#6.2.4">6.2.4</a> strtoul function, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.20.1.2">7.20.1.2</a>,
24965 storage order of array, <a href="#6.5.2.1">6.5.2.1</a> <a href="#7.20.1.4">7.20.1.4</a>, <a href="#7.24.2.2">7.24.2.2</a>
24966 storage-class specifiers, <a href="#6.7.1">6.7.1</a>, <a href="#6.11.5">6.11.5</a> strtoull function, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.20.1.2">7.20.1.2</a>, <a href="#7.20.1.4">7.20.1.4</a>
24967 strcat function, <a href="#7.21.3.1">7.21.3.1</a> strtoumax function, <a href="#7.8.2.3">7.8.2.3</a>
24970 strcoll function, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.21.4.3">7.21.4.3</a>, <a href="#7.21.4.5">7.21.4.5</a> arrow operator (->), <a href="#6.5.2.3">6.5.2.3</a>
24972 strcspn function, <a href="#7.21.5.3">7.21.5.3</a> dot operator (.), <a href="#6.5.2.3">6.5.2.3</a>
24973 streams, <a href="#7.19.2">7.19.2</a>, <a href="#7.20.4.3">7.20.4.3</a> initialization, <a href="#6.7.8">6.7.8</a>
24976 orientation, <a href="#7.19.2">7.19.2</a> member operator (.), <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.2.3">6.5.2.3</a>
24977 standard error, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.3">7.19.3</a> pointer operator (->), <a href="#6.5.2.3">6.5.2.3</a>
24978 standard input, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.3">7.19.3</a> specifier, <a href="#6.7.2.1">6.7.2.1</a>
24979 standard output, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.3">7.19.3</a> tag, <a href="#6.2.3">6.2.3</a>, <a href="#6.7.2.3">6.7.2.3</a>
24980 unbuffered, <a href="#7.19.3">7.19.3</a> type, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.2.1">6.7.2.1</a>
24981 strerror function, <a href="#7.19.10.4">7.19.10.4</a>, <a href="#7.21.6.2">7.21.6.2</a> strxfrm function, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.21.4.5">7.21.4.5</a>
24982 strftime function, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.23.3">7.23.3</a>, <a href="#7.23.3.5">7.23.3.5</a>, subscripting, <a href="#6.5.2.1">6.5.2.1</a>
24983 <a href="#7.24.5.1">7.24.5.1</a> subtraction assignment operator (-=), <a href="#6.5.16.2">6.5.16.2</a>
24984 <!--page 550 -->
24985 subtraction operator (-), <a href="#6.5.6">6.5.6</a>, <a href="#F.3">F.3</a>, <a href="#G.5.2">G.5.2</a> tolower function, <a href="#7.4.2.1">7.4.2.1</a>
24987 floating constant, <a href="#6.4.4.2">6.4.4.2</a> towctrans function, <a href="#7.25.3.2.1">7.25.3.2.1</a>, <a href="#7.25.3.2.2">7.25.3.2.2</a>
24988 integer constant, <a href="#6.4.4.1">6.4.4.1</a> towlower function, <a href="#7.25.3.1.1">7.25.3.1.1</a>, <a href="#7.25.3.2.1">7.25.3.2.1</a>
24989 switch body, <a href="#6.8.4.2">6.8.4.2</a> towupper function, <a href="#7.25.3.1.2">7.25.3.1.2</a>, <a href="#7.25.3.2.1">7.25.3.2.1</a>
24990 switch case label, <a href="#6.8.1">6.8.1</a>, <a href="#6.8.4.2">6.8.4.2</a> translation environment, <a href="#5">5</a>, <a href="#5.1.1">5.1.1</a>
24991 switch default label, <a href="#6.8.1">6.8.1</a>, <a href="#6.8.4.2">6.8.4.2</a> translation limits, <a href="#5.2.4.1">5.2.4.1</a>
24992 switch statement, <a href="#6.8.1">6.8.1</a>, <a href="#6.8.4.2">6.8.4.2</a> translation phases, <a href="#5.1.1.2">5.1.1.2</a>
24993 swprintf function, <a href="#7.24.2.3">7.24.2.3</a>, <a href="#7.24.2.7">7.24.2.7</a> translation unit, <a href="#5.1.1.1">5.1.1.1</a>, <a href="#6.9">6.9</a>
24994 swscanf function, <a href="#7.24.2.4">7.24.2.4</a>, <a href="#7.24.2.8">7.24.2.8</a> trap representation, <a href="#6.2.6.1">6.2.6.1</a>, <a href="#6.2.6.2">6.2.6.2</a>, <a href="#6.3.2.3">6.3.2.3</a>,
24997 syntax notation, <a href="#6.1">6.1</a> complex, <a href="#7.3.5">7.3.5</a>, <a href="#G.6.1">G.6.1</a>
24998 syntax rule precedence, <a href="#5.1.1.2">5.1.1.2</a> real, <a href="#7.12.4">7.12.4</a>, <a href="#F.9.1">F.9.1</a>
24999 syntax summary, language, <a href="#A">A</a> trigraph sequences, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#5.2.1.1">5.2.1.1</a>
25002 tab characters, <a href="#5.2.1">5.2.1</a>, <a href="#6.4">6.4</a> trunc type-generic macro, <a href="#7.22">7.22</a>
25003 tag compatibility, <a href="#6.2.7">6.2.7</a> truncation, <a href="#6.3.1.4">6.3.1.4</a>, <a href="#7.12.9.8">7.12.9.8</a>, <a href="#7.19.3">7.19.3</a>, <a href="#7.19.5.3">7.19.5.3</a>
25005 tags, <a href="#6.7.2.3">6.7.2.3</a> two's complement, <a href="#6.2.6.2">6.2.6.2</a>, <a href="#7.18.1.1">7.18.1.1</a>
25006 tan functions, <a href="#7.12.4.7">7.12.4.7</a>, <a href="#F.9.1.7">F.9.1.7</a> type category, <a href="#6.2.5">6.2.5</a>
25007 tan type-generic macro, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</a> type conversion, <a href="#6.3">6.3</a>
25008 tanh functions, <a href="#7.12.5.6">7.12.5.6</a>, <a href="#F.9.2.6">F.9.2.6</a> type definitions, <a href="#6.7.7">6.7.7</a>
25009 tanh type-generic macro, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</a> type domain, <a href="#6.2.5">6.2.5</a>, <a href="#G.2">G.2</a>
25012 text streams, <a href="#7.19.2">7.19.2</a>, <a href="#7.19.7.11">7.19.7.11</a>, <a href="#7.19.9.2">7.19.9.2</a>, <a href="#7.19.9.4">7.19.9.4</a> type qualifiers, <a href="#6.7.3">6.7.3</a>
25013 tgamma functions, <a href="#7.12.8.4">7.12.8.4</a>, <a href="#F.9.5.4">F.9.5.4</a> type specifiers, <a href="#6.7.2">6.7.2</a>
25014 tgamma type-generic macro, <a href="#7.22">7.22</a> type-generic macro, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</a>
25015 tgmath.h header, <a href="#7.22">7.22</a>, <a href="#G.7">G.7</a> typedef declaration, <a href="#6.7.7">6.7.7</a>
25017 broken down, <a href="#7.23.1">7.23.1</a>, <a href="#7.23.2.3">7.23.2.3</a>, <a href="#7.23.3">7.23.3</a>, <a href="#7.23.3.1">7.23.3.1</a>, types, <a href="#6.2.5">6.2.5</a>
25018 <a href="#7.23.3.3">7.23.3.3</a>, <a href="#7.23.3.4">7.23.3.4</a>, <a href="#7.23.3.5">7.23.3.5</a> character, <a href="#6.7.8">6.7.8</a>
25019 calendar, <a href="#7.23.1">7.23.1</a>, <a href="#7.23.2.2">7.23.2.2</a>, <a href="#7.23.2.3">7.23.2.3</a>, <a href="#7.23.2.4">7.23.2.4</a>, compatible, <a href="#6.2.7">6.2.7</a>, <a href="#6.7.2">6.7.2</a>, <a href="#6.7.3">6.7.3</a>, <a href="#6.7.5">6.7.5</a>
25020 <a href="#7.23.3.2">7.23.3.2</a>, <a href="#7.23.3.3">7.23.3.3</a>, <a href="#7.23.3.4">7.23.3.4</a> complex, <a href="#6.2.5">6.2.5</a>, <a href="#G">G</a>
25022 conversion functions, <a href="#7.23.3">7.23.3</a> const qualified, <a href="#6.7.3">6.7.3</a>
25025 manipulation functions, <a href="#7.23.2">7.23.2</a> restrict qualified, <a href="#6.7.3">6.7.3</a>
25026 time function, <a href="#7.23.2.4">7.23.2.4</a> volatile qualified, <a href="#6.7.3">6.7.3</a>
25029 tm structure type, <a href="#7.23.1">7.23.1</a>, <a href="#7.24.1">7.24.1</a> UINT_FASTN_MAX macros, <a href="#7.18.2.3">7.18.2.3</a>
25030 TMP_MAX macro, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.4.3">7.19.4.3</a>, <a href="#7.19.4.4">7.19.4.4</a> uint_fastN_t types, <a href="#7.18.1.3">7.18.1.3</a>
25031 tmpfile function, <a href="#7.19.4.3">7.19.4.3</a>, <a href="#7.20.4.3">7.20.4.3</a> UINT_LEASTN_MAX macros, <a href="#7.18.2.2">7.18.2.2</a>
25032 tmpnam function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.4.3">7.19.4.3</a>, <a href="#7.19.4.4">7.19.4.4</a> uint_leastN_t types, <a href="#7.18.1.2">7.18.1.2</a>
25033 token, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#6.4">6.4</a>, see also preprocessing tokens UINT_MAX macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>
25034 token concatenation, <a href="#6.10.3.3">6.10.3.3</a> UINTMAX_C macro, <a href="#7.18.4.2">7.18.4.2</a>
25035 token pasting, <a href="#6.10.3.3">6.10.3.3</a> UINTMAX_MAX macro, <a href="#7.8.2.3">7.8.2.3</a>, <a href="#7.8.2.4">7.8.2.4</a>, <a href="#7.18.2.5">7.18.2.5</a>
25036 <!--page 551 -->
25037 uintmax_t type, <a href="#7.18.1.5">7.18.1.5</a>, <a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.19.6.2">7.19.6.2</a>, USHRT_MAX macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>
25038 <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a> usual arithmetic conversions, <a href="#6.3.1.8">6.3.1.8</a>, <a href="#6.5.5">6.5.5</a>, <a href="#6.5.6">6.5.6</a>,
25039 UINTN_C macros, <a href="#7.18.4.1">7.18.4.1</a> <a href="#6.5.8">6.5.8</a>, <a href="#6.5.9">6.5.9</a>, <a href="#6.5.10">6.5.10</a>, <a href="#6.5.11">6.5.11</a>, <a href="#6.5.12">6.5.12</a>, <a href="#6.5.15">6.5.15</a>
25040 UINTN_MAX macros, <a href="#7.18.2.1">7.18.2.1</a> utilities, general, <a href="#7.20">7.20</a>
25043 uintptr_t type, <a href="#7.18.1.4">7.18.1.4</a> va_arg macro, <a href="#7.15">7.15</a>, <a href="#7.15.1">7.15.1</a>, <a href="#7.15.1.1">7.15.1.1</a>, <a href="#7.15.1.2">7.15.1.2</a>,
25044 ULLONG_MAX macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#7.20.1.4">7.20.1.4</a>, <a href="#7.15.1.4">7.15.1.4</a>, <a href="#7.19.6.8">7.19.6.8</a>, <a href="#7.19.6.9">7.19.6.9</a>, <a href="#7.19.6.10">7.19.6.10</a>,
25045 <a href="#7.24.4.1.2">7.24.4.1.2</a> <a href="#7.19.6.11">7.19.6.11</a>, <a href="#7.19.6.12">7.19.6.12</a>, <a href="#7.19.6.13">7.19.6.13</a>, <a href="#7.19.6.14">7.19.6.14</a>,
25046 ULONG_MAX macro, <a href="#5.2.4.2.1">5.2.4.2.1</a>, <a href="#7.20.1.4">7.20.1.4</a>, <a href="#7.24.2.5">7.24.2.5</a>, <a href="#7.24.2.6">7.24.2.6</a>, <a href="#7.24.2.7">7.24.2.7</a>, <a href="#7.24.2.8">7.24.2.8</a>,
25047 <a href="#7.24.4.1.2">7.24.4.1.2</a> <a href="#7.24.2.9">7.24.2.9</a>, <a href="#7.24.2.10">7.24.2.10</a>
25048 unary arithmetic operators, <a href="#6.5.3.3">6.5.3.3</a> va_copy macro, <a href="#7.15">7.15</a>, <a href="#7.15.1">7.15.1</a>, <a href="#7.15.1.1">7.15.1.1</a>, <a href="#7.15.1.2">7.15.1.2</a>,
25050 unary minus operator (-), <a href="#6.5.3.3">6.5.3.3</a>, <a href="#F.3">F.3</a> va_end macro, <a href="#7.1.3">7.1.3</a>, <a href="#7.15">7.15</a>, <a href="#7.15.1">7.15.1</a>, <a href="#7.15.1.3">7.15.1.3</a>,
25051 unary operators, <a href="#6.5.3">6.5.3</a> <a href="#7.15.1.4">7.15.1.4</a>, <a href="#7.19.6.8">7.19.6.8</a>, <a href="#7.19.6.9">7.19.6.9</a>, <a href="#7.19.6.10">7.19.6.10</a>,
25052 unary plus operator (+), <a href="#6.5.3.3">6.5.3.3</a> <a href="#7.19.6.11">7.19.6.11</a>, <a href="#7.19.6.12">7.19.6.12</a>, <a href="#7.19.6.13">7.19.6.13</a>, <a href="#7.19.6.14">7.19.6.14</a>,
25053 unbuffered stream, <a href="#7.19.3">7.19.3</a> <a href="#7.24.2.5">7.24.2.5</a>, <a href="#7.24.2.6">7.24.2.6</a>, <a href="#7.24.2.7">7.24.2.7</a>, <a href="#7.24.2.8">7.24.2.8</a>,
25054 undef preprocessing directive, <a href="#6.10.3.5">6.10.3.5</a>, <a href="#7.1.3">7.1.3</a>, <a href="#7.24.2.9">7.24.2.9</a>, <a href="#7.24.2.10">7.24.2.10</a>
25055 <a href="#7.1.4">7.1.4</a> va_list type, <a href="#7.15">7.15</a>, <a href="#7.15.1.3">7.15.1.3</a>
25056 undefined behavior, <a href="#3.4.3">3.4.3</a>, <a href="#4">4</a>, <a href="#J.2">J.2</a> va_start macro, <a href="#7.15">7.15</a>, <a href="#7.15.1">7.15.1</a>, <a href="#7.15.1.1">7.15.1.1</a>,
25057 underscore character, <a href="#6.4.2.1">6.4.2.1</a> <a href="#7.15.1.2">7.15.1.2</a>, <a href="#7.15.1.3">7.15.1.3</a>, <a href="#7.15.1.4">7.15.1.4</a>, <a href="#7.19.6.8">7.19.6.8</a>,
25058 underscore, leading, in identifier, <a href="#7.1.3">7.1.3</a> <a href="#7.19.6.9">7.19.6.9</a>, <a href="#7.19.6.10">7.19.6.10</a>, <a href="#7.19.6.11">7.19.6.11</a>, <a href="#7.19.6.12">7.19.6.12</a>,
25059 ungetc function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.7.11">7.19.7.11</a>, <a href="#7.19.9.2">7.19.9.2</a>, <a href="#7.19.6.13">7.19.6.13</a>, <a href="#7.19.6.14">7.19.6.14</a>, <a href="#7.24.2.5">7.24.2.5</a>, <a href="#7.24.2.6">7.24.2.6</a>,
25060 <a href="#7.19.9.3">7.19.9.3</a> <a href="#7.24.2.7">7.24.2.7</a>, <a href="#7.24.2.8">7.24.2.8</a>, <a href="#7.24.2.9">7.24.2.9</a>, <a href="#7.24.2.10">7.24.2.10</a>
25061 ungetwc function, <a href="#7.19.1">7.19.1</a>, <a href="#7.24.3.10">7.24.3.10</a> value, <a href="#3.17">3.17</a>
25064 arrow operator (->), <a href="#6.5.2.3">6.5.2.3</a> variable arguments header, <a href="#7.15">7.15</a>
25065 content, <a href="#6.7.2.3">6.7.2.3</a> variable length array, <a href="#6.7.5">6.7.5</a>, <a href="#6.7.5.2">6.7.5.2</a>
25066 dot operator (.), <a href="#6.5.2.3">6.5.2.3</a> variably modified type, <a href="#6.7.5">6.7.5</a>, <a href="#6.7.5.2">6.7.5.2</a>
25067 initialization, <a href="#6.7.8">6.7.8</a> vertical-tab character, <a href="#5.2.1">5.2.1</a>, <a href="#6.4">6.4</a>
25068 member alignment, <a href="#6.7.2.1">6.7.2.1</a> vertical-tab escape sequence (\v), <a href="#5.2.2">5.2.2</a>, <a href="#6.4.4.4">6.4.4.4</a>,
25070 member operator (.), <a href="#6.3.2.1">6.3.2.1</a>, <a href="#6.5.2.3">6.5.2.3</a> vfprintf function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.6.8">7.19.6.8</a>
25071 pointer operator (->), <a href="#6.5.2.3">6.5.2.3</a> vfscanf function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.6.8">7.19.6.8</a>, <a href="#7.19.6.9">7.19.6.9</a>
25072 specifier, <a href="#6.7.2.1">6.7.2.1</a> vfwprintf function, <a href="#7.19.1">7.19.1</a>, <a href="#7.24.2.5">7.24.2.5</a>
25073 tag, <a href="#6.2.3">6.2.3</a>, <a href="#6.7.2.3">6.7.2.3</a> vfwscanf function, <a href="#7.19.1">7.19.1</a>, <a href="#7.24.2.6">7.24.2.6</a>, <a href="#7.24.3.10">7.24.3.10</a>
25074 type, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.2.1">6.7.2.1</a> visibility of identifier, <a href="#6.2.1">6.2.1</a>
25077 unqualified version of type, <a href="#6.2.5">6.2.5</a> void function parameter, <a href="#6.7.5.3">6.7.5.3</a>
25078 unsigned integer suffix, u or <a href="#U">U</a>, <a href="#6.4.4.1">6.4.4.1</a> void type, <a href="#6.2.5">6.2.5</a>, <a href="#6.3.2.2">6.3.2.2</a>, <a href="#6.7.2">6.7.2</a>
25079 unsigned integer types, <a href="#6.2.5">6.2.5</a>, <a href="#6.3.1.3">6.3.1.3</a>, <a href="#6.4.4.1">6.4.4.1</a> void type conversion, <a href="#6.3.2.2">6.3.2.2</a>
25080 unsigned type conversion, <a href="#6.3.1.1">6.3.1.1</a>, <a href="#6.3.1.3">6.3.1.3</a>, volatile storage, <a href="#5.1.2.3">5.1.2.3</a>
25081 <a href="#6.3.1.4">6.3.1.4</a>, <a href="#6.3.1.8">6.3.1.8</a> volatile type qualifier, <a href="#6.7.3">6.7.3</a>
25082 unsigned types, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.2">6.7.2</a>, <a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.19.6.2">7.19.6.2</a>, volatile-qualified type, <a href="#6.2.5">6.2.5</a>, <a href="#6.7.3">6.7.3</a>
25083 <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a> vprintf function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.6.8">7.19.6.8</a>, <a href="#7.19.6.10">7.19.6.10</a>
25084 unspecified behavior, <a href="#3.4.4">3.4.4</a>, <a href="#4">4</a>, <a href="#J.1">J.1</a> vscanf function, <a href="#7.19.1">7.19.1</a>, <a href="#7.19.6.8">7.19.6.8</a>, <a href="#7.19.6.11">7.19.6.11</a>
25085 unspecified value, <a href="#3.17.3">3.17.3</a> vsnprintf function, <a href="#7.19.6.8">7.19.6.8</a>, <a href="#7.19.6.12">7.19.6.12</a>
25086 uppercase letter, <a href="#5.2.1">5.2.1</a> vsprintf function, <a href="#7.19.6.8">7.19.6.8</a>, <a href="#7.19.6.13">7.19.6.13</a>
25087 use of library functions, <a href="#7.1.4">7.1.4</a> vsscanf function, <a href="#7.19.6.8">7.19.6.8</a>, <a href="#7.19.6.14">7.19.6.14</a>
25088 <!--page 552 -->
25089 vswprintf function, <a href="#7.24.2.7">7.24.2.7</a> wctype.h header, <a href="#7.25">7.25</a>, <a href="#7.26.13">7.26.13</a>
25090 vswscanf function, <a href="#7.24.2.8">7.24.2.8</a> wctype_t type, <a href="#7.25.1">7.25.1</a>, <a href="#7.25.2.2.2">7.25.2.2.2</a>
25091 vwprintf function, <a href="#7.19.1">7.19.1</a>, <a href="#7.24.2.9">7.24.2.9</a> WEOF macro, <a href="#7.24.1">7.24.1</a>, <a href="#7.24.3.1">7.24.3.1</a>, <a href="#7.24.3.3">7.24.3.3</a>, <a href="#7.24.3.6">7.24.3.6</a>,
25092 vwscanf function, <a href="#7.19.1">7.19.1</a>, <a href="#7.24.2.10">7.24.2.10</a>, <a href="#7.24.3.10">7.24.3.10</a> <a href="#7.24.3.7">7.24.3.7</a>, <a href="#7.24.3.8">7.24.3.8</a>, <a href="#7.24.3.9">7.24.3.9</a>, <a href="#7.24.3.10">7.24.3.10</a>,
25095 wchar.h header, <a href="#5.2.4.2.2">5.2.4.2.2</a>, <a href="#7.19.1">7.19.1</a>, <a href="#7.24">7.24</a>, <a href="#7.26.12">7.26.12</a>, white space, <a href="#5.1.1.2">5.1.1.2</a>, <a href="#6.4">6.4</a>, <a href="#6.10">6.10</a>, <a href="#7.4.1.10">7.4.1.10</a>,
25097 WCHAR_MAX macro, <a href="#7.18.3">7.18.3</a>, <a href="#7.24.1">7.24.1</a> white-space characters, <a href="#6.4">6.4</a>
25098 WCHAR_MIN macro, <a href="#7.18.3">7.18.3</a>, <a href="#7.24.1">7.24.1</a> wide character, <a href="#3.7.3">3.7.3</a>
25099 wchar_t type, <a href="#3.7.3">3.7.3</a>, <a href="#6.4.4.4">6.4.4.4</a>, <a href="#6.4.5">6.4.5</a>, <a href="#6.7.8">6.7.8</a>, case mapping functions, <a href="#7.25.3.1">7.25.3.1</a>
25100 <a href="#6.10.8">6.10.8</a>, <a href="#7.17">7.17</a>, <a href="#7.18.3">7.18.3</a>, <a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.20">7.20</a>, extensible, <a href="#7.25.3.2">7.25.3.2</a>
25101 <a href="#7.24.1">7.24.1</a>, <a href="#7.24.2.1">7.24.2.1</a>, <a href="#7.24.2.2">7.24.2.2</a> classification functions, <a href="#7.25.2.1">7.25.2.1</a>
25102 wcrtomb function, <a href="#7.19.3">7.19.3</a>, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.2">7.24.2.2</a>, extensible, <a href="#7.25.2.2">7.25.2.2</a>
25103 <a href="#7.24.6.3.3">7.24.6.3.3</a>, <a href="#7.24.6.4.2">7.24.6.4.2</a> constant, <a href="#6.4.4.4">6.4.4.4</a>
25104 wcscat function, <a href="#7.24.4.3.1">7.24.4.3.1</a> formatted input/output functions, <a href="#7.24.2">7.24.2</a>
25105 wcschr function, <a href="#7.24.4.5.1">7.24.4.5.1</a> input functions, <a href="#7.19.1">7.19.1</a>
25106 wcscmp function, <a href="#7.24.4.4.1">7.24.4.4.1</a>, <a href="#7.24.4.4.4">7.24.4.4.4</a> input/output functions, <a href="#7.19.1">7.19.1</a>, <a href="#7.24.3">7.24.3</a>
25107 wcscoll function, <a href="#7.24.4.4.2">7.24.4.4.2</a>, <a href="#7.24.4.4.4">7.24.4.4.4</a> output functions, <a href="#7.19.1">7.19.1</a>
25108 wcscpy function, <a href="#7.24.4.2.1">7.24.4.2.1</a> single-byte conversion functions, <a href="#7.24.6.1">7.24.6.1</a>
25109 wcscspn function, <a href="#7.24.4.5.2">7.24.4.5.2</a> wide string, <a href="#7.1.1">7.1.1</a>
25110 wcsftime function, <a href="#7.11.1.1">7.11.1.1</a>, <a href="#7.24.5.1">7.24.5.1</a> wide string comparison functions, <a href="#7.24.4.4">7.24.4.4</a>
25111 wcslen function, <a href="#7.24.4.6.1">7.24.4.6.1</a> wide string concatenation functions, <a href="#7.24.4.3">7.24.4.3</a>
25112 wcsncat function, <a href="#7.24.4.3.2">7.24.4.3.2</a> wide string copying functions, <a href="#7.24.4.2">7.24.4.2</a>
25113 wcsncmp function, <a href="#7.24.4.4.3">7.24.4.4.3</a> wide string literal, see string literal
25114 wcsncpy function, <a href="#7.24.4.2.2">7.24.4.2.2</a> wide string miscellaneous functions, <a href="#7.24.4.6">7.24.4.6</a>
25115 wcspbrk function, <a href="#7.24.4.5.3">7.24.4.5.3</a> wide string numeric conversion functions, <a href="#7.8.2.4">7.8.2.4</a>,
25117 wcsrtombs function, <a href="#7.24.6.4.2">7.24.6.4.2</a> wide string search functions, <a href="#7.24.4.5">7.24.4.5</a>
25118 wcsspn function, <a href="#7.24.4.5.5">7.24.4.5.5</a> wide-oriented stream, <a href="#7.19.2">7.19.2</a>
25120 wcstod function, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.2">7.24.2.2</a> WINT_MAX macro, <a href="#7.18.3">7.18.3</a>
25121 wcstod function, <a href="#7.24.4.1.1">7.24.4.1.1</a> WINT_MIN macro, <a href="#7.18.3">7.18.3</a>
25122 wcstof function, <a href="#7.24.4.1.1">7.24.4.1.1</a> wint_t type, <a href="#7.18.3">7.18.3</a>, <a href="#7.19.6.1">7.19.6.1</a>, <a href="#7.24.1">7.24.1</a>, <a href="#7.24.2.1">7.24.2.1</a>,
25124 wcstok function, <a href="#7.24.4.5.7">7.24.4.5.7</a> wmemchr function, <a href="#7.24.4.5.8">7.24.4.5.8</a>
25125 wcstol function, <a href="#7.8.2.4">7.8.2.4</a>, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.2">7.24.2.2</a>, wmemcmp function, <a href="#7.24.4.4.5">7.24.4.4.5</a>
25127 wcstold function, <a href="#7.24.4.1.1">7.24.4.1.1</a> wmemmove function, <a href="#7.24.4.2.4">7.24.4.2.4</a>
25128 wcstoll function, <a href="#7.8.2.4">7.8.2.4</a>, <a href="#7.24.4.1.2">7.24.4.1.2</a> wmemset function, <a href="#7.24.4.6.2">7.24.4.6.2</a>
25129 wcstombs function, <a href="#7.20.8.2">7.20.8.2</a>, <a href="#7.24.6.4">7.24.6.4</a> wprintf function, <a href="#7.19.1">7.19.1</a>, <a href="#7.24.2.9">7.24.2.9</a>, <a href="#7.24.2.11">7.24.2.11</a>
25130 wcstoul function, <a href="#7.8.2.4">7.8.2.4</a>, <a href="#7.19.6.2">7.19.6.2</a>, <a href="#7.24.2.2">7.24.2.2</a>, wscanf function, <a href="#7.19.1">7.19.1</a>, <a href="#7.24.2.10">7.24.2.10</a>, <a href="#7.24.2.12">7.24.2.12</a>,
25136 wctomb function, <a href="#7.20.7.3">7.20.7.3</a>, <a href="#7.20.8.2">7.20.8.2</a>, <a href="#7.24.6.3">7.24.6.3</a>
25140 </pre>
25141 </body></html>